Fixes and improvements

Fixed a bug where Rotato could crash if you right clicked a scene to update it
Fixed a bug where pressing Cmd+3 would crash Rotato
Fixed a bug where Rotato would apply a subtle environment to .rotato files saved in previous versions where environments were turned off
Fixed a bug where Rotato would crash if you dragged in non-relevant files
Fixed a bug where Rotato could crash when trying to download a scene with no internet connection
Fixed a bug where Rotato could crash on macOS 11 and 12 when opening a scene with no device screen contents
Fixed a bug where Rotato could crash if you opened a .rotato document with no animations and tried to adjust the movie length
Fixed a bug where Rotato could crash if you tried to add animations to specific App Store image templates