Aside from making the logic clearer, this avoids a call to
warn_dangling_symrefs(), which always does a for_each_rawref()
iteration.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>