x/tools/gopls: toGobDiagnostic bug reported by telemetry

[adonovan]

This stack XvsbEA was reported by telemetry:

gopls/bug
golang.org/x/tools/gopls/internal/bug.report:35
golang.org/x/tools/gopls/internal/bug.Errorf:2
golang.org/x/tools/gopls/internal/lsp/cache.(*action).exec.func2:11
golang.org/x/tools/gopls/internal/lsp/cache.toGobDiagnostic:22
golang.org/x/tools/gopls/internal/lsp/cache.(*action).exec.func3:1
honnef.co/go/tools/analysis/report.Report:25
honnef.co/go/tools/staticcheck.CheckTypedNilInterface:100
golang.org/x/tools/gopls/internal/lsp/cache.(*action).exec.func6:31
golang.org/x/tools/gopls/internal/lsp/cache.(*action).exec:177
golang.org/x/tools/gopls/internal/lsp/cache.execActions.func1.1:2
sync.(*Once).doSlow:5
sync.(*Once).Do:?65
golang.org/x/tools/gopls/internal/lsp/cache.execActions.func1:2
runtime.goexit:0

golang.org/x/tools/gopls@v0.14.2 go1.21.4 darwin/arm64 other,vscode-insiders (1)

Issue created by golang.org/x/tools/gopls/internal/telemetry/cmd/stacks.

This stack 9SSGkw was reported by telemetry:

gopls/bug
golang.org/x/tools/gopls/internal/bug.report:35
golang.org/x/tools/gopls/internal/bug.Reportf:1
golang.org/x/tools/gopls/internal/lsp/cache.(*action).exec.func3:3
honnef.co/go/tools/analysis/report.Report:25
honnef.co/go/tools/staticcheck.CheckTypedNilInterface:100
golang.org/x/tools/gopls/internal/lsp/cache.(*action).exec.func6:31
golang.org/x/tools/gopls/internal/lsp/cache.(*action).exec:177
golang.org/x/tools/gopls/internal/lsp/cache.execActions.func1.1:2
sync.(*Once).doSlow:5
sync.(*Once).Do:?65
golang.org/x/tools/gopls/internal/lsp/cache.execActions.func1:2
runtime.goexit:0

golang.org/x/tools/gopls@v0.14.2 go1.21.4 darwin/arm64 other,vscode-insiders (1)

Issue created by golang.org/x/tools/gopls/internal/telemetry/cmd/stacks.

[adonovan]

Dup of #64547.