Long worm may get killed in middle of action

If long worm attacks you, and you have a passive response that may
kill the worm (eg. blue jelly), the worm may die in the middle of
a loop checking for a worm segment that can attack. This'll cause
a segfault because the worm segments will get freed.

If the worm dies, just exit the loop.

src/worm.c

@@ -301,7 +301,8 @@ register struct monst *worm;
      */
     for (seg = wtails[wnum]; seg; seg = seg->nseg)
         if (distu(seg->wx, seg->wy) < 3)
-            (void) mattacku(worm);
+            if (mattacku(worm))
+                return; /* your passive ability killed the worm */
 }
 
 /*  cutworm()