Fix tests

Author: elliette

packages/devtools_app/lib/src/standalone_ui/ide_shared/property_editor/property_editor_view.dart

@@ -52,7 +52,7 @@ class PropertyEditorView extends StatelessWidget {
 
         final (:properties, :name, :documentation, :fileUri) =
             editableWidgetData;
-        if (fileUri == null || !fileUri.endsWith('.dart')) {
+        if (fileUri != null && !fileUri.endsWith('.dart')) {
           return const CenteredMessage(
             message: 'No Dart code found at the current cursor location.',
           );

packages/devtools_app/test/standalone_ui/ide_shared/property_editor/property_editor_test.dart

@@ -99,6 +99,7 @@ void main() {
           ),
         ).thenAnswer((realInvocation) {
           getEditableArgsCalled?.complete();
+          getEditableArgsCalled = Completer<void>();
           return Future.value(result);
         });
       }