Protect Artwork from deletion if it still has images.

Author: Greg Turner

collectionkit/contrib/work_creator/models/image.py

@@ -64,7 +64,7 @@ def order_by_view(self):
 
 class WorkImageBase(models.Model):
 
-    artwork = models.ForeignKey('collection.Artwork', related_name='images')
+    artwork = models.ForeignKey('collection.Artwork', related_name='images', on_delete=models.PROTECT)
 
     order = models.PositiveIntegerField(null=True, blank=True)