TF-4236 Fix guard delete UI when no handler is provided.

integration_test/robots/email_robot.dart

@@ -88,6 +88,11 @@ class EmailRobot extends CoreRobot {
   }
 
   Future<void> tapRemoveLabelButton(String labelDisplayName) async {
-    await $(EmailSubjectWidget).$(LabelWidget).$(TagWidget).$(InkWell).tap();
+    await $(EmailSubjectWidget)
+        .$(LabelWidget)
+        .$(TagWidget)
+        .which<TagWidget>((widget) => widget.text == labelDisplayName)
+        .$(InkWell)
+        .tap();
   }
 }

integration_test/robots/thread_robot.dart

@@ -42,6 +42,7 @@ class ThreadRobot extends CoreRobot {
     );
     await $.waitUntilVisible(email);
     await email.tap();
+    await $.pump(const Duration(seconds: 2));
   }
 
   Future<void> openMailbox() async {