[BUG] Gorm, -refreshCells in GormImageEditor.m

[Sungjin Chun]

Hi,

Line 586 in GormImageEditor has [[self superview] bounds].size.width, 
but for my case(I'm using art backend) when
I select Open or New from menu, Gorm.app dies with Segmentation Fault. 
After adding line if (![self superview]) return;
so that if [self superview] does return nil, it just returns and not 
accessing results of -bound method call. I do not know
whether xlib backend has same problem. Please fix this.

Thanks in advance.