[releng] autosigner: Add missing check for None

[Till Maas]

commit 15384d725b1508c18301adac3be722c4a68a7fe2
Author: Till Maas 
Date:   Mon Nov 10 20:40:38 2014 +0100

autosigner: Add missing check for None

scripts/autosigner.py |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/scripts/autosigner.py b/scripts/autosigner.py
index 4b07008..5ca2a42 100755
--- a/scripts/autosigner.py
+++ b/scripts/autosigner.py
@@ -272,7 +272,9 @@ class AutoSigner(object):
             self.signers[signer_id] = signer

signing_task = signer.sign(signing_task=signing_task)
-        if signing_task.unsigned:
+        if signing_task is not None:
+            return False
+        elif signing_task.unsigned:
             signing_task.error_count += 1
             signing_task.last_attempt = time.time()
             self.incomplete.append(signing_task)