Allow importing without images

[omgitsraven]

I'm trying to open an .lwo file that references a number of textures; I actually have the textures, but unfortunately their filenames have been somewhat scrambled by accent encoding problems... I was hoping to just assign them by hand, however, the script currently just sits in a loop complaining that it can't find the folder for any of them.

I've worked around this by simply commenting out the for c_id in self.clips: loop, but it might be convenient if the 'cancel' button would allow importing the meshes textureless rather than abandoning the import completely.

[dreisicht]

+1