Invalid internal object names cause issue on loading .readcom files

[birbilis]

Version: 0.5.12

when one adds an image with "-" in its filename, the resulting object name stored inside the .readcom file will contain a "-" which makes it an invalid name. Should fix the code that sanitizes those object names so that invalid object names never get saved in the .readcom files

Also should try to load such invalid objects if possible and fix the name on load.