update script/gen_gallery.py to skip missing images
update script/gen_gallery.py to skip missing images

lokik/sfepy,vlukes/sfepy,vlukes/sfepy,RexFuzzle/sfepy,rc/sfepy,RexFuzzle/sfepy,BubuLK/sfepy,lokik/sfepy,rc/sfepy,sfepy/sfepy,rc/sfepy,vlukes/sfepy,RexFuzzle/sfepy,sfepy/sfepy,BubuLK/sfepy,lokik/sfepy,RexFuzzle/sfepy,BubuLK/sfepy,sfepy/sfepy,lokik/sfepy