PlugIn Management: No warning about unsaved changes

Description of problem:
When you make changes to some plugin and then you click on close button, warning about unsaved changes doesn't appear. After plugin reopening, all unsaved data are not present.

Version-Release number of selected component (if applicable):
6.1.0-DR4

How reproducible:
-

Steps to Reproduce:
1. Create some plugin. (for example: PlugIn Management -> New... -> New Perspective)
2. Add some text to text boxes.
3. Click on 'x' (close) button.

Actual results:
Warning doesn't appear and plugin editor is closed.

Expected results:
Warning appears.

Additional info:
-