oc-rtf: Be more resilient to spaces while parsing font tables

This avoids to crash on this example:

  \f0\fibi \fcharset0
   -------^

Or:

  \f0 \fibi\fcharset0
   --^

Take into account that I found lots of RTF documents with this format:

  \f0\fbidi \froman\fcharset0
  \f0\froman\fprq2 \fcharset0

Which are not unsupported by this handler.