fix: 浏览器禁用站点数据时面板不再白屏，坏帧不再重置看门狗

web-admin/src/App.tsx

@@ -52,7 +52,14 @@ const DARK_MEDIA = matchMedia("(prefers-color-scheme: dark)")
  * listener is otherwise never heard, and the next one is a day away.
  */
 function useTheme() {
-  const [saved, setSaved] = useState(() => localStorage.getItem("theme"))
+  // Storage can be switched off for the site, and then even reading it throws.
+  const [saved, setSaved] = useState(() => {
+    try {
+      return localStorage.getItem("theme")
+    } catch {
+      return null
+    }
+  })
   const system = useSyncExternalStore(
     (notify) => {
       DARK_MEDIA.addEventListener("change", notify)
@@ -80,7 +87,11 @@ function useTheme() {
     dark,
     () => {
       const next = dark ? "light" : "dark"
-      localStorage.setItem("theme", next)
+      try {
+        localStorage.setItem("theme", next)
+      } catch {
+        // The choice then lasts until the page is closed.
+      }
       setSaved(next)
     },
   ] as const

web-admin/src/lib/api.ts

@@ -534,11 +534,19 @@ export function useNodes() {
         }, 10_000)
       }
       watch()
+      // Only a frame that parses re-arms the watchdog, so a stream whose frames
+      // cannot be read counts as silent and is replaced.
       opened.onmessage = (event) => {
+        let nodes, admin
+        try {
+          ;({ nodes, admin } = JSON.parse(event.data))
+        } catch (e) {
+          console.warn("live frame dropped:", e)
+          return
+        }
         watch()
-        const frame = JSON.parse(event.data)
-        setNodes(frame.nodes)
-        setAdmin(frame.admin)
+        setNodes(nodes)
+        setAdmin(admin)
         setError(null)
         // The stream has returned; the poll was only covering for it.
         if (poll) {