[Camera] Unable to move or zoom after object deletion

Steps needed to confirm and replicate:
1. Zoom in or out with camera. (To verify camera movement.)
2. Select an object within the map. (Tested with pyramids and boxes)
3. `Object` menu -> `Delete Selected` to delete object.
4. Attempt to zoom in or out with camera. (Camera does not zoom.)

What resolves this:
* Switching to another tab and back again
* Opening and hovering over a menu option before going to the 3D world view.

An observation to be noted:
In the `Object` menu, `Clear Selection` and `Delete Selected` may not be selected/are faded out when this occurs. Interesting enough, they remain faded out even if zoom works, but become re-enabled when an object is selected.