Cannot save project if EP is not assigned to test bed about twister

[bogdanpopescu]

@CJHoffmann we cannot reproduce this; please indicate the GUI applet version

[CJHoffmann]

Create a new TB, but do not assign an EP to it.

Create a project with the new TB assigned to it.

Save the project and note the popup message. No indication why the save failed.

Assign an EP to the TB.

Saving the project is now successful.

GUI Version:

[CJHoffmann]

When a project is saved, a warning is now declared if any test suite is assigned to a SUT that does not have an EP assigned to it. The project file is saved.
Works as expected.