fix black screen issue

lib/src/utils/misc.dart

@@ -210,6 +210,10 @@ Future<bool> authenticateUser(
         return true;
       }
     }
+  } catch (e) {
+    // Catch unexpected platform exceptions (e.g. PlatformException) that
+    // would otherwise propagate and leave callers in a broken state.
+    Log.error('Unexpected authentication error: $e');
   }
   return false;
 }

lib/src/visual/views/chats/media_viewer.view.dart

@@ -671,6 +671,25 @@ class _MediaViewerViewState extends State<MediaViewerView> {
           child: Stack(
             fit: StackFit.expand,
             children: [
+              // Fallback: when no content is visible (no media, no loader,
+              // no twonly-present overlay), show a loader to prevent a
+              // black screen. If there are truly no files left, exit.
+              if (!_showDownloadingLoader &&
+                  currentMedia == null &&
+                  videoController == null &&
+                  !displayTwonlyPresent)
+                Builder(builder: (context) {
+                  // Schedule exit on the next frame if there is nothing
+                  // left to display, so we don't trap the user.
+                  if (allMediaFiles.isEmpty) {
+                    WidgetsBinding.instance.addPostFrameCallback((_) {
+                      if (mounted && currentMedia == null) {
+                        Navigator.of(context).maybePop();
+                      }
+                    });
+                  }
+                  return _loader();
+                }),
               if (_showDownloadingLoader) _loader(),
               if ((currentMedia != null || videoController != null) &&
                   (canBeSeenUntil == null || progress.value >= 0))