fixed a problem with computed fields

gluon/dal.py

@@ -7396,11 +7396,8 @@ class Table(dict):
                 elif update and not ofield.update is None:
                     new_fields.append((ofield,ofield.update))
         for ofield in self:
-            if not ofield.name in new_fields_names and ofield.compute:
-                try:
-                    new_fields.append((ofield,ofield.compute(Row(fields))))
-                except KeyError:
-                    pass
+            if ofield.compute:
+                new_fields.append((ofield,ofield.compute(Row(fields))))
             if not update and ofield.required and not ofield.name in new_fields_names:
                 raise SyntaxError,'Table: missing required field: %s' % ofield.name
         return new_fields