Fixed item creation with full inventory (#2914)

* Fixes #2858.
* Prevented items from being created if adding them to the inventory failed for whatever reason.
* Introduced a new config that allows to keep the old behavior.
Thanks to @Artuvazro and @Daegaladh!

src/map/battle.cpp

@@ -8494,6 +8494,7 @@ static const struct _battle_data {
 	{ "event_refine_chance",                &battle_config.event_refine_chance,             0,      0,      1,              },
 	{ "autoloot_adjust",                    &battle_config.autoloot_adjust,                 0,      0,      1,              },
 	{ "broadcast_hide_name",                &battle_config.broadcast_hide_name,             2,      0,      NAME_LENGTH,    },
+	{ "skill_drop_items_full",              &battle_config.skill_drop_items_full,           0,      0,      1,              },
 
 #include "../custom/battle_config_init.inc"
 };