Fix: Loading data

lib/components/my_button.dart

@@ -1,10 +1,10 @@
 import 'package:flutter/material.dart';
 
 class MyButton extends StatelessWidget {
-  void Function()? onTap;
+  final void Function()? onTap;
   final String text;
 
-  MyButton({
+  const MyButton({
     super.key,
     required this.text,
     required this.onTap,

lib/pages/user_data_page.dart

@@ -59,14 +59,20 @@ class _UserDataPageState extends State<UserDataPage> {
           .doc(currentUserId)
           .get();
 
+      if (!userSnapshot.exists || userSnapshot.data() == null) {
+        return; // should not happen, user entry should exist
+      }
+
+      Map<String, dynamic> userFields =
+          userSnapshot.data() as Map<String, dynamic>;
+
       // Extract gender and birth year
+      if (userFields.containsKey(Constants.dbFieldUsersGender)) {
         _genderFromDb = userSnapshot[Constants.dbFieldUsersGender];
-      _yearFromDb = userSnapshot
+      }
-              .data()
+      if (userFields.containsKey(Constants.dbFieldUsersYearBorn)) {
-              .toString()
+        _yearFromDb = userSnapshot[Constants.dbFieldUsersYearBorn];
-              .contains(Constants.dbFieldUsersYearBorn)
+      }
-          ? userSnapshot[Constants.dbFieldUsersYearBorn]
-          : null;
 
       // Fetch locations
       QuerySnapshot locationSnapshot = await _firestore
@@ -391,6 +397,7 @@ class _UserDataPageState extends State<UserDataPage> {
                     : 'undefined'),
                 const SizedBox(width: 20),
                 DropdownMenu(
+                  initialSelection: _selectedYear,
                   onSelected: (int? newValue) {
                     setState(() {
                       _selectedYear = newValue;
@@ -403,7 +410,6 @@ class _UserDataPageState extends State<UserDataPage> {
                     );
                   }),
                   label: const Text('birth year'),
-                  initialSelection: _yearFromDb,
                 ),
               ],
             ),