Comment 2 for bug 654191

I can reproduce this bug. Here are the steps I used to reproduce it:
1) Connect with XChat and Konversation to the same server
2) Join the same channel
3) Use Konversation to change the topic to "Testing"
4) /part the channel in XChat
5) Change the topic to an empty string in Konversation
6) Rejoin the channel in XChat, the topic in the tooltip is still Testing.