Possible bug in documentation.cc (de-referencing nullpointer)

[Andreas Weber]

Dear Torsten,

I write directly to you because you've added the code with cset 
ba5af45bbfc4 and I hope you can help quickly. If you are busy I'll 
create a bugreport for this.

In documentation.cc:78 m_help_engine is create with new and can't be 
NULL after this (except on VC6) so the check in line 110 isn't needed 
but after this it's set to 0 (line 112) and de-referenced afterwards 
(for example line 177, 181, 186 and so on)
which results in a SIGSEGV (signal 11)

Thank you, Andy