Pass in the expected type to readObject anywhere the code would clearly convert the wrong type to null anyway

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5440 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/presents/client/Communicator.as

@@ -236,7 +236,7 @@ public class Communicator
         _inStream.setSource(frameData);
         var msg :DownstreamMessage;
         try {
-            msg = (_inStream.readObject() as DownstreamMessage);
+            msg = (_inStream.readObject(DownstreamMessage) as DownstreamMessage);
         } catch (e :Error) {
             log.warning("Error processing downstream message: " + e);
             log.logStackTrace(e);