validate form before saving

lib/pages/task_edit_page.dart

@@ -191,6 +191,7 @@ class _TaskEditPageState extends State<TaskEditPage> {
   }
 
   void onSavePressed() {
+    if (formKey.currentState!.validate()) {
       Navigator.of(context).pop(
         CreateTaskRequest(
           title: titleController.text,
@@ -218,6 +219,7 @@ class _TaskEditPageState extends State<TaskEditPage> {
         ),
       );
     }
+  }
 
   void onPopInvoked(bool didPop, Object? result) {
     if (!didPop) {