review: guard refreshMaterialAboutList with isAdded (avoid null adapter)

Per Greptile: if the fragment is detached while the battery-settings screen is open,
the activity-result callback's refreshMaterialAboutList() could dereference a null
adapter. Guard with isAdded, matching the checkUpdate() pattern.

Author: hawkff

app/src/main/java/io/nekohasekai/sagernet/ui/AboutFragment.kt

@@ -52,7 +52,9 @@ class AboutFragment : ToolbarFragment(R.layout.layout_about) {
             // The battery-optimization request/settings screen returns RESULT_CANCELED even
             // when the user actually granted the exemption, so don't gate on the result code
             // — just rebuild the list so the item's on/off subtext reflects the new state.
-            refreshMaterialAboutList()
+            // Guard with isAdded: the fragment may be detached while the settings screen was
+            // open, and refreshMaterialAboutList() would otherwise touch a null adapter.
+            if (isAdded) refreshMaterialAboutList()
         }
 
         override fun getMaterialAboutList(activityContext: Context): MaterialAboutList {