If we skip an object because it does not have a bounding box, retrigger the change timer

This causes the platform physics to run again a few ms later so that we actually do not
stop trying to push objects apart until everything is correctly updated

Fixes Asana issue 33694499624771

cura/PlatformPhysics.py

@@ -49,6 +49,7 @@ class PlatformPhysics:
 
             bbox = node.getBoundingBox()
             if not bbox or not bbox.isValid():
+                self._change_timer.start()
                 continue
 
             # Mark the node as outside the build volume if the bounding box test fails.