fix: handle undefined TSS_PRERENDABLE_PATHS in prerender function

Author: FatahChan

packages/start-plugin-core/src/global.d.ts

@@ -3,6 +3,6 @@ import type { Manifest } from '@tanstack/router-core'
 /* eslint-disable no-var */
 declare global {
   var TSS_ROUTES_MANIFEST: Manifest
-  var TSS_PRERENDABLE_PATHS: Array<{ path: string }>
+  var TSS_PRERENDABLE_PATHS: Array<{ path: string }> | undefined
 }
 export {}

packages/start-plugin-core/src/prerender.ts

@@ -28,9 +28,10 @@ export async function prerender({
 
     if (startConfig.prerender.autoStaticPathsDiscovery ?? true) {
       // merge discovered static pages with user-defined pages
-      const pagesMap = new Map(pages.map((item) => [item.path, item]))
+      const pagesMap = new Map(pages.map(item => [item.path, item]));
+      const discoveredPages = globalThis.TSS_PRERENDABLE_PATHS || [];
 
-      for (const page of globalThis.TSS_PRERENDABLE_PATHS) {
+      for (const page of discoveredPages) {
         if (!pagesMap.has(page.path)) {
           pagesMap.set(page.path, page)
         }