[Lazarus] Fix for broken scrollbar in lhelp (fix in turbopower_ipro)

[Bernd Kreuss]

> Is in possible to cancel the dialog in the BeforeExecute event, my plan 
> was to ask the user to save the current file (Yes/No/Cancel) before 
> opening another.

Cannot you check if the current file needs to be saved and prompt the 
user for it _before_ opening the dialog?

Cheers, A.