Don't show empty help categories

[ForNeVeR]

Consider this:

<xxx> $help
<horta hell> xxx: Доступные команды для текущего уровня доступа (Общий):
• Markov: ......... say, s
• KarmaPlugin: .... karma
• Wtf: ............ wtf, wtf-delete
• HtmlReader: ..... link
• Diagnostic: ..... 
• Visitor: ........ 
• Version: ........ version
• Loglist: ........ loglist
• Mail: ........... send
• Pet: ............ pet
• Fortune: ........ fortune
• Helper: ......... man, help
• Dice: ........... dice
• Bash: ........... bash
• Log: ............ search
• Access: ......... access

There should be no categories such as Diagnostic or Visitor in the output.