Fix another "no monster to remove" impossible

Pet ranged attack code was using the same variable for
both pet attacking a monster and then the monster's possible
retaliation attack. The retaliation obviously overwrote the
pet attack return code, allowing pet to move afterwards.
In certain case this could result in "no monster to remove"
warning.

src/dogmove.c

@@ -917,8 +917,9 @@ pet_ranged_attk(struct monst *mtmp)
                  * if it's blind or unseeing, it can't retaliate
                  */
                 if (mtarg->mcansee && haseyes(mtarg->data)) {
-                    mstatus = mattackm(mtarg, mtmp);
-                    if (mstatus & M_ATTK_DEF_DIED)
+                    int mresp = mattackm(mtarg, mtmp);
+
+                    if (mresp & M_ATTK_DEF_DIED)
                         return MMOVE_DIED;
                 }
             }