Fixed a minor bug that could cause crashing when modifying a single file.

Fixed a MAJOR bug that was setting "VisibilityMultiplier" of chassisdef files to 0. This would render the mech practically invisible.

Future Update:
I noticed an issue where you could modify a single file, then do a batch edit which includes that file, and return to the single edit mode to find that the displayed values were from before the batch edit. You have to reload the file to see the new values. I wanted to get the other fixes out right away, but I will work on this in the future.