Demo at https://demo.fyne.io crashed when clicking "Light" in bottom left.

[redawl]

Steps to reproduce:

1. Open https://demo.fyne.io in firefox
2. Click the "Light" button in the bottom left.
3. In the console, you'll see a stack trace printed, and "Uncaught Error: Go program has already exited" will be printed as a console error. Additionally, the site becomes unresponsive.

[andydotxyz]

Can you include the stack trace here please? That is the important part for tracking down the issue

[redawl]

2025/06/23 16:37:04 Lifecycle: Entered Foreground [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
panic: syscall/js: call of Value.Call on null [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
<empty string> [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
goroutine 1 [running]: [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
syscall/js.Value.Call({{}, 0x7ff8000000000002, 0x0}, {0x1ebd37, 0xd}, {0x18336d8, 0x1, 0x1}) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/usr/lib/golang/src/syscall/js/js.go:438 +0x3f [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
github.com/fyne-io/gl-js.DeleteTexture(...) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/github.com/fyne-io/gl-js@v0.1.0/gl_webgl_wasm.go:303 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/painter/gl.(*xjsContext).DeleteTexture(0x16c6040, {{{}, 0x7ff80001000000b1, 0x2c9c838}}) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/painter/gl/gl_wasm.go:135 +0x4 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/painter/gl.(*painter).getTexture.func1() [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/painter/gl/texture.go:53 +0x6 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/cache.DeleteTextTexturesFor.func1({{{0x2c54c00, 0x7}, 0x41600000, {0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, {0x0, ...}}, ...}, ...) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/cache/texture_common.go:82 +0x11 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/cache.DeleteTextTexturesFor.(*Map[...]).Range.func2({0xf6c00, 0x195be00}) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/async/map.go:60 +0x8 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
internal/sync.(*HashTrieMap[...]).iter(0x4dee60, 0x2c8f4a0, 0x1833940) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/usr/lib/golang/src/internal/sync/hashtriemap.go:512 +0x1f [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
internal/sync.(*HashTrieMap[...]).Range(0x4dee60, 0x1833940) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/usr/lib/golang/src/internal/sync/hashtriemap.go:495 +0xe [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
sync.(*Map).Range(0x16b5c20, 0x1833940) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/usr/lib/golang/src/sync/hashtriemap.go:115 +0x4 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/async.(*Map[...]).Range(...) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/async/map.go:59 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/cache.DeleteTextTexturesFor({0x4d45d0, 0x1a7d680}) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/cache/texture_common.go:79 +0x4 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*window).RescaleContext(0x1801a40) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/window_wasm.go:497 +0x9 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*glCanvas).reloadScale(0x1a7d680) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/canvas.go:183 +0xe [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*gLDriver).runGL.func1.1({0x4d5460, 0x1801a40}) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/loop.go:115 +0x7 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/app.ApplySettingsWithCallback({0x4cf0f8, 0x1a88dd0}, {0x4d4270, 0x1a798c0}, 0x3efdc8) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/app/theme.go:48 +0x19 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*gLDriver).runGL.func1({0x4cf0f8, 0x1a88dd0}) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/loop.go:109 +0x5 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/app.(*settings).apply(0x1a88dd0) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/app/settings.go:122 +0xe [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/app.(*settings).applyTheme(...) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/app/settings.go:87 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/app.(*settings).SetTheme(0x1a88dd0, {0x4ca720, 0x1941848}) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/app/settings.go:73 +0x8 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
main.makeNav.func7() [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/tmp/tmp.5HZRUkPg4p/main.go:256 +0x19 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/widget.(*Button).Tapped(0x1877b90, 0x2eeb0c0) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/widget/button.go:188 +0x9 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*window).mouseClickedHandleTapDoubleTap(0x1801a40, {0x4ceeb8, 0x1877b90}, 0x2eeb0c0) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/window.go:589 +0x21 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*window).processMouseClicked(0x1801a40, 0x1, 0x0, 0x0) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/window.go:550 +0xa2 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*window).mouseClicked-fm.(*window).mouseClicked.func1() [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/window_wasm.go:212 +0x4 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*gLDriver).runGL(0x1a79810) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/loop.go:135 +0x36 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*gLDriver).Run(0x1a79810) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/driver.go:162 +0x8 [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/app.(*fyneApp).Run(0x1a798c0) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/app/app.go:77 +0x1b [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
fyne.io/fyne/v2/internal/driver/glfw.(*window).ShowAndRun(0x1801a40) [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/var/home/jacob/go/pkg/mod/fyne.io/fyne/v2@v2.6.0/internal/driver/glfw/window.go:222 +0xc [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
main.main() [wasm_exec.js:22:14](https://demo.fyne.io/wasm_exec.js)
	/tmp/tmp.5HZRUkPg4p/main.go:80 +0x6b

Are you having trouble reproducing? I didn't include it originally because of how trivial the steps to reproduce are.

[andydotxyz]

Thanks for that.

I could not see it until I knew what to look for for some reason - anyhow it's always good go get the stack if available so we are on the same page :)