When a form which is embedded in a Landing Page is deleted (using the Form Manager page), we are supposed to display a message about it.
Currently there are two messages that are presented (it appears that they are displayed randomly, or perhaps there is a race condition somewhere).

Steps to reproduce:
1. Login as admin
2. Navigate to "Page" tab
3. Create a new Landing Page with layout_1.
4. Add a Form block and cofigure it.
5. Navigate to Content -> Form Manager page.
6. Delete the newly added Form.
7. Go to "Page" tab, navigate to the created Landing Page
8. Switch multiple (10) times between View and Edit modes.

Expected behaviour:
The following message is displayed every time: message1 attachment

Actual behaviour:
Sometimes the correct message is displayed, sometimes other one is visible: message2 attachment.