Merge "Fix newrev comparison for NullChange"
diff --git a/zuul/scheduler.py b/zuul/scheduler.py
index 6627677..292ed30 100644
--- a/zuul/scheduler.py
+++ b/zuul/scheduler.py
@@ -30,7 +30,7 @@
 import layoutvalidator
 import model
 from model import ActionReporter, Pipeline, Project, ChangeQueue
-from model import EventFilter, ChangeishFilter
+from model import EventFilter, ChangeishFilter, NullChange
 from zuul import change_matcher
 from zuul import version as zuul_version
 
@@ -1529,7 +1529,8 @@
         if event.merged:
             build_set.commit = event.commit
         elif event.updated:
-            build_set.commit = item.change.newrev
+            if not isinstance(item, NullChange):
+                build_set.commit = item.change.newrev
         if not build_set.commit:
             self.log.info("Unable to merge change %s" % item.change)
             self.pipeline.setUnableToMerge(item)