Crash on changing element font color in Workflow Designer

Scenario:

1. Open the WD.
2. Add an element to the scene. Select it.
3. Select "Element properties" -> "Background color" in the context menu.
   Expected state: the "Color" dialog appears.
4. Select any color, accept the dialog.
5. Select "Element properties" -> "Font" in the context menu.
   Expected state: the "Select Font" dialog appears (currently, it is native).
6. Click the button to select the font color.
   Expected state: a modal dialog to select color appears.
   Current state: a dialog to select color appears. It is not modal. It has "Ok" and "Cancel" buttons.
7. Select any color, accept the dialog.
   Current state: UGENE crashes.

Fix the crash.

Check, if there should be a possibility to change the color. If there isn't, then forbid to call color selecting dialog.
If you skip the step with the background color changing, then the font color selecting dialog won't have "Ok" and "Cancel" buttons. Fix it if there will be a possibility to call this dialog.