fixed possible lockups on app start

test/storage/in_memory_storage_test.dart

@@ -0,0 +1,21 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/storage/hydrated_storage_bootstrap.dart';
+
+void main() {
+  test('InMemoryStorage round-trips, deletes and clears', () async {
+    final storage = InMemoryStorage();
+    expect(storage.read('a'), isNull);
+
+    await storage.write('a', {'x': 1});
+    await storage.write('b', 'two');
+    expect(storage.read('a'), {'x': 1});
+    expect(storage.read('b'), 'two');
+
+    await storage.delete('a');
+    expect(storage.read('a'), isNull);
+    expect(storage.read('b'), 'two');
+
+    await storage.clear();
+    expect(storage.read('b'), isNull);
+  });
+}