BUG: Fix short circuit in StateTransform loop.

A missing `continue` statement was causing the short circuit on
event type to not have the intended effect of skipping the update
portion of the loop.

zipline/transforms/utils.py

@@ -144,6 +144,7 @@ class StatefulTransform(object):
                         DATASOURCE_TYPE.TRADE,
                         DATASOURCE_TYPE.CUSTOM)):
                 yield message
+                continue
             # allow upstream generators to yield None to avoid
             # blocking.
             if message is None: