The "Remove tool" button state isn't updated in case of selecting ET throught the Line Edit

Scenario:

1. Open the "External tools" tab in the "Preferences" dialod
2. Choose any validated tool, select the path to it in the line edit, cut and click to another line (the last action starts a validation task)
   Expected state: The "Remove tool" button became disabled
   Current state: The "Remove tool" button still enabled
3. Click to the "Remove tool" button
4. Paste the path to the tool from the clipboard to this line edit again and click to another line
   Expected state: The "Remove tool" button became enabled
   Current state: The "Remove tool" button still disabled