geometry should be updated before deleting it

[Marius Stanciu]

If I create a new geometry, add some objects and then delete the geometry file in the left project panel without hitting first the 'OK' update geometry button, the program will be stuck in the geometry editing until a new empty geometry is created, the OK update button is pressed and then we can safely delete the geometry file from the the project panel.

When deleting a geometry file the program should make sure that the geometry is updated. If not, it should issue at least a warning or better, perform the update and then issue a delete command.