Two consecutive emtpy messages confuse message size tracking

[0xabadea]

When _trackMessageSize() is invoked with the first empty message, the while loop breaks immediately because message.length == 0. Then the "if (messages.length == 0" line after the while loop adds the message to response.partialMessage, so its value becomes "0<|msg|>" (the message delimiter is "<|msg|>" in wicket-atmosphere). The function returns true, so the message is not passed to callbacks.

When the function is invoked with the second empty message, the new message is appended to partialMessage, which now has the value "0<|msg|>0<|msg|>". This then confuses the substring-based parsing, which now only adds one empty message to the messages array, and this time the function returns false.

The point of this issue is that the first empty message should be delivered to callback immediately. If you're thinking "why are they sending empty messages", wicket-atmosphere does that. If sending empty messages in a bug in wicket-atmosphere (I believe it is), it is masked by this Atmosphere bug, or at least its first occurrence is.

[0xabadea]

Wicket issue: https://issues.apache.org/jira/browse/WICKET-5153

[jfarcand]

Since the WICKET issue is fixed, closing this issue.