Fix: hatching wielded/quivered egg called weight()

According to vanilla code, it is not a bug for setnotworn to be called
with a hatching egg that has already had its quan changed to 0. So this
fixes it inside setworn, only recalculating the object's weight if it
was worn armor. (If someone manages to wear an egg as armor, that will
be a worse bug than this.)

src/worn.c

@@ -135,7 +135,11 @@ setnotworn(struct obj *obj)
             p = armor_provides_extrinsic(obj);
             u.uprops[p].extrinsic = u.uprops[p].extrinsic & ~wp->w_mask;
             obj->owornmask &= ~wp->w_mask;
-            obj->owt = weight(obj); /* remove armor weight reduction */
+            if (wp->w_mask & W_ARMOR)
+                /* this function can technically be called with wielded or
+                 * quivered egg in the process of hatching, which is not worn
+                 * armor */
+                obj->owt = weight(obj); /* remove armor weight reduction */
             if (obj->oartifact)
                 set_artifact_intrinsic(obj, 0, wp->w_mask);
             if ((p = w_blocks(obj, wp->w_mask)) != 0)