Fix test

Author: m-kuhn

tests/src/python/test_provider_postgres.py

@@ -479,7 +479,7 @@ def testTransactionConstrains(self):
 
         # check new values
         self.assertTrue(vl.getFeatures('id=1').nextFeature(f))
-        self.assertEqual(f.attributes(), [1, 1, NULL])
+        self.assertEqual(f.attributes(), [1, 1, 0])
 
     def testTransactionTuple(self):
         # create a vector layer based on postgres