This was partially handled by ungetting the end group token (i.e. '}')
so that it was read again at the proper place.  Unfortunately there is a
read hook that maintains a stackTop variable, which is decremented when
receiving this end group token.  Therefore stackTop would get
decremented twice, and the rich text file would end prematurely.

This is fixed by incrementing the stackTop variable to compensate for it
being decremented twice.