mod switch between pages and remove errors

lib/widgets/my_form_field.dart

@@ -18,8 +18,36 @@ class MyFormField extends StatelessWidget {
   final TextInputType keyboardType;
   final String? Function(String?)? validator;
 
+  // Prüft ob Controller noch verwendbar ist
+  bool _isControllerValid() {
+    try {
+      userController.text;
+      return true;
+    } catch (e) {
+      return false;
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
+    // Wenn Controller disposed ist, zeige Ersatz-Widget
+    if (!_isControllerValid()) {
+      return Container(
+        height: 56,
+        decoration: BoxDecoration(
+          color: fillColor,
+          borderRadius: BorderRadius.circular(4),
+          border: Border.all(color: Colors.grey),
+        ),
+        child: Center(
+          child: Text(
+            '$labelText (Controller nicht verfügbar)',
+            style: TextStyle(color: Colors.grey[600]),
+          ),
+        ),
+      );
+    }
+
     return TextFormField(
       autovalidateMode: AutovalidateMode.onUserInteraction,
       style: const TextStyle(color: Colors.black),