Guard Against Message of NoneType (#315)

diff --git a/provider/consumer.py b/provider/consumer.py
index 865c209..84e1e2d 100644
--- a/provider/consumer.py
+++ b/provider/consumer.py
@@ -479,6 +479,9 @@
             except UnicodeDecodeError:
                 logging.warn('[{}] Value contains non-unicode bytes. Replacing invalid bytes.'.format(self.trigger))
                 value = unicode(value, errors='replace').encode('utf-8')
+        except AttributeError:
+           logging.warn('[{}] Cannot decode a NoneType message value'.format(self.trigger))
+           return value
 
         if self.encodeValueAsJSON:
             try: