Existing widget name error from rejected widget object.

Rejected widget object for paste action from other widget somehow remains in the widget editor making name conflict for other widgets.

1) Create 2 widgets, Name it a and b
2) Create a button in widget (a), Name it as TestButton
3) Copy (TestButton)
4) Create a Border in (b)
5) Add an image as its child
6) Try paste (TestButton) as the border's child
Expected=Result: Toast will be popped up with following message:
Can't paste contents, not enough available slots in target widget.
7) Add a new button under Canvas panel, Name it TestButton to see there is any conflict following existing name.
Expected: Newly added Button have its name changed as TestButton in Widget (b)
Result: Existing widget name error shows up in the text box.
8) Undo changing button's name
9) Save the widget (b)
10) Close Widget window (b)
11) reopen the widget (b)
12) Try change newly added button's name as TestButton again.
Expected=Result: The button's name is changed as TestButton in Widget (b)