fixed widget mounting errors

lib/view/pages/absence_report/absence_report_view.dart

@@ -165,23 +165,28 @@ class _AbsenceReportViewState extends State<AbsenceReportView> {
   Widget _buildBody(BuildContext context) => FutureBuilder<void>(
     future: _init,
     builder: (context, snapshot) {
-        if (snapshot.connectionState != ConnectionState.done) {
-          return const Center(child: AppProgressIndicator.large());
-        }
-        if (snapshot.hasError) {
-          return PlaceholderView(
-            icon: Icons.error_outline,
-            text: errorToUserMessage(snapshot.error),
-            button: ElevatedButton.icon(
-              onPressed: () => setState(() => _init = _load()),
-              icon: const Icon(Icons.refresh),
-              label: const Text('Erneut versuchen'),
-            ),
-          );
-        }
-        return _buildForm(context);
-      },
-    );
+      if (snapshot.connectionState != ConnectionState.done) {
+        return const Center(child: AppProgressIndicator.large());
+      }
+      if (snapshot.hasError) {
+        return PlaceholderView(
+          icon: Icons.error_outline,
+          text: errorToUserMessage(snapshot.error),
+          button: ElevatedButton.icon(
+            onPressed: () {
+              final reload = _load();
+              setState(() {
+                _init = reload;
+              });
+            },
+            icon: const Icon(Icons.refresh),
+            label: const Text('Erneut versuchen'),
+          ),
+        );
+      }
+      return _buildForm(context);
+    },
+  );
 
   Widget _buildForm(BuildContext context) {
     final theme = Theme.of(context);

lib/widget/user_avatar.dart

@@ -230,11 +230,15 @@ class _UserAvatarState extends State<UserAvatar> {
 
     final pending = _pendingAvatars.putIfAbsent(url, () {
       final future = _fetch(url);
-      future.whenComplete(() {
-        if (identical(_pendingAvatars[url], future)) {
-          _pendingAvatars.remove(url);
-        }
-      });
+      // Cleanup hangs off an error-neutralised copy: whenComplete on `future`
+      // itself returns a second future that forwards the error unawaited.
+      unawaited(
+        future.then<void>((_) {}, onError: (_) {}).whenComplete(() {
+          if (identical(_pendingAvatars[url], future)) {
+            _pendingAvatars.remove(url);
+          }
+        }),
+      );
       return future;
     });