Made IrcState handle empty TOPIC correctly.
Made IrcState handle empty TOPIC correctly.

prashantpawar/supybot-rothbot,mazaclub/mazabot-core,mazaclub/mazabot-core,haxwithaxe/supybot,ProgVal/Limnoria-test,frumiousbandersnatch/supybot-code,Ban3/Limnoria,buildbot/supybot,raboof/supybot,ProgVal/Limnoria-test,Ban3/Limnoria,kblin/supybot-gsoc,jeffmahoney/supybot