RTF importer - Minor fix (PATCH)

Thanks to Hubert for pointing this out. I managed to misread "Helvetic" as
"Helvetica". This is a (one line) patch against the current CVS-HEAD.
(I.e. the version Martin committed).

Hub: If you ever want to use the bytebuf patch please add a "fn[0][8] =
'\0';" or equivalent, as appropriate.

Best wishes,

R.