Image: prevent useless object modification when self.data has 0 length

product/ERP5/Document/Image.py

@@ -150,9 +150,9 @@ class Image(TextConvertableMixin, File, OFSImage):
       self.data = self._data
 
     # Make sure size is defined
-    if (not hasattr(aq_base(self), 'size') or not self.size) and \
-                      hasattr(aq_base(self), 'data'):
-      self.size = len(self.data)
+    size = len(self.data)
+    if getattr(aq_base(self), 'size', None) != size:
+      self.size = size
 
   security.declareProtected(Permissions.AccessContentsInformation, 'getWidth')
   def getWidth(self):