fixed: Try to recache image in case cached texture loading fails

Up till now we didn't handle failed texture loading for cached images. This could occur in cases where the locally cached file is missing (or corrupt) and possibly other scenarios. 
Well corruption can happen due to local filesystem errors, network issues and issues on the remote server. In my case it occurred because of filesystem issues, and currently we will never ever recover from that which means the user has to completely (and manually!) remove their texture database file.