Fix: impossible "trying to break non-equipped glass obj?" when attack…

…ing with certain objects.

Discovered this whilst fuzzing. The hero was attacking monsters with a
wielded paper object (scroll, spellbook). One particular monster it
attacked was a flaming sphere, which blows up once killed, and will
cause fire damage to random objects in inventory. Things like spellbooks
and scrolls will burn up instantly - when that happened while said
scroll or spellbook was being wielded, it caused an impossible in
break_glass_obj().

The fix - guard against materials that don't technically break.

doc/evilhack-changelog.md

@@ -4357,4 +4357,6 @@ The following changes to date are:
 - Fix: the Riders/Wizard of Yendor should not be able to open any locked
   container
 - Fix: wizkill command vs dmonsfree
+- Fix: impossible "trying to break non-equipped glass obj?" when
+  attacking with certain objects
 

src/dothrow.c

@@ -2670,9 +2670,9 @@ boolean in_view;
 
 /* Possibly destroy a glass object by its use in melee or thrown combat.
  * Return TRUE if destroyed.
- * Separate logic from breakobj because we are not unconditionally breaking the
- * object, and we also need to make sure it's removed from the inventory
- * properly. */
+ * Separate logic from breakobj because we are not unconditionally
+ * breaking the object, and we also need to make sure it's removed from
+ * the inventory properly. */
 boolean
 break_glass_obj(obj)
 struct obj* obj;
@@ -2685,6 +2685,15 @@ struct obj* obj;
     if (!obj)
         return FALSE;
 
+    /* guard against objects that can never break
+       or go 'splat!' */
+    if (!(obj->material == GLASS
+          || obj->material == FLESH
+          || obj->material == VEGGY
+          || obj->material == ADAMANTINE
+          || obj->forged_qual == FQ_INFERIOR))
+        return FALSE;
+
     ucarried = carried(obj);
 
     if (ucarried) {