fix steed-in-trap message grammar when hallucinating

fix steed-in-trap message grammar when hallucinating

     Fix the recently reported bug about the wording of trap messsages
when hero's steed has a name but hallucination prevents that name from
being used, yielding "You lead poor wombat into a pit!" and the like.

     I accidentally deleted the message so can't reply to the sender.

[Before applying this patch, take a look at the POLY_TRAP case of the
switch statement in steedintrap().  A misplaced brace has drawn the
default case into one of its `if' statements.  Evidently it's valid C
syntax, but someone among us must have access to a compiler or lint
checking tool which is capable to diagnosing such things.]