[2.0.7] Crash when enabling Snap to Grid in empty blueprint

[whompratt]

To reproduce:

a. Alt-B to put a new empty blueprint in hand
b. Click and drag over _some objects_
c. In the configuration UI that opens, right-click items to remove them until blueprint is empty
d. Click "snap to grid" and crash should occur

Expected typical blueprint snapping behaviour but with no objects present, just an empty green indicator.

[Rseding91]

Thanks for the report. This is now fixed for the next release.