Don't clear the message box after validation error

[mmuller]

Found in version 1.6.2

Steps:
Go to create a new Reminder
Don't fill the Title field
Add an External Action
Save the External Action
Press the button to save the form

Obtained:
The External Action is removed and you have to select a new Externa Action

Expected:
The External Action is not removed after validation error

Additional info:
This happens using External Actions and messages