avoid #wizrumorcheck crash on bad rumor input

avoid #wizrumorcheck crash on bad rumor input

If either rumors.tru or rumors.fal was empty when makedefs made
'rumors', init_rumors() will set true_rumor_size to -1 to indicate
that rumors aren't available.  It also closes the input file, and
then #wizrumorcheck closed that again, triggering a crash in the
dlb code.

Fortune cookies and oracles work ok (just not very interesting)
when rumors aren't available.  Only the check command had trouble
with that.