function repairable_damage() in shk.c was dereferencing a pointer
argument prior to a subsequent check for a NULL pointer that
resulted in an early function return (pr #671 by argrath)
+function savelev() in save.c was dereferencing a NHFILE pointer for
+ nhfp->mode prior to a subsequent check for nhfp being NULL
+ to trigger a call to panic() if it was; move the check for NULL
+ above that usage (pr #675 by argrath)
+function tin_details() in eat.c was passing an obj pointer to
+ tin_variety() where it was dereferenced; move the tin_details()
+ NULL check above that tin_variety() call (pr #676 by argrath)
Code Cleanup and Reorganization