static analyzer bit for makemon.c

src/makemon.c(918): warning: Dereferencing NULL pointer '((mon))->mextra'.

src/makemon.c

@@ -914,8 +914,10 @@ clone_mon(struct monst *mon,
            However, tamedog() will not re-tame a tame dog, so m2
            must be made non-tame to get initialized properly. */
         m2->mtame = 0;
-        if (tamedog(m2, (struct obj *) 0))
+        if (tamedog(m2, (struct obj *) 0)) {
+            assert(has_edog(m2));
             *EDOG(m2) = *EDOG(mon);
+        }
         /* [TODO? some (most? all?) edog fields probably should be
            reinitialized rather that retain the 'parent's values] */
     }