work around collide not returning false with a null object

[Azaezel]

fix a crash caused by having boundingBoxCollision on, while projecting the mouse so that there is nothing between it and a globalbounds object it would seem we're somehow ending up in a state of WorldEditor::collide returning true it hit somethging, but NULL as far as what until we properly fix this, doublecheck to make sure the hitObject isn't NULL before we start trying to reference membervars/methods