Deleting a bound function from a widget sets the binding to None which causes compile to fail

Deleting a bound function from a widget sets the binding to None which causes compile to fail.

Deleting a bound function from a widget sets the binding to None which causes compile to fail

The links in the Compiler Results log put focus on the Viewport. The binding can be removed to eliminate the compile error.

Reproduced in 4.7.2 binary and Main (//depot/UE4/Promotable-CL-2471062)

1. Open any project
2. Create a new Widget Blueprint
3. Add a Text widget
4. Create Binding
5. In the Graph's My Blueprint tab, delete the resulting function
6. Compile

Result:
Compile fails with:

Error Binding: Property ' TextDelegate ' on Widget ' TextBlock_109 ': Binding: 'None' : 'None' was not found on 'New Widget Blueprint'.