Added test for empty nested command.
Added test for empty nested command.

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