fix flayers inability to deploy swarmprod

code/modules/antagonists/mind_flayer/powers/flayer_weapon_powers.dm

@@ -38,7 +38,7 @@
 		create_new_weapon()
 	weapon_ref.flags |= (ABSTRACT | NODROP) // Just in case the item doesn't start with both of these, or somehow loses them.
 
-	if(!user.drop_item() || HAS_TRAIT(user, TRAIT_HANDS_BLOCKED))
+	if(HAS_TRAIT(user, TRAIT_HANDS_BLOCKED) || (user.get_active_hand() && !user.drop_item()))
 		flayer.send_swarm_message("We cannot manifest [weapon_ref] into our active hand...")
 		return FALSE
 
@@ -53,8 +53,7 @@
 	SIGNAL_HANDLER // COMSIG_MOB_WILLINGLY_DROP + COMSIG_FLAYER_RETRACT_IMPLANTS
 	if(!any_hand && !istype(owner.get_active_hand(), weapon_type))
 		return
-	INVOKE_ASYNC(owner, TYPE_PROC_REF(/mob, drop_item_to_ground), weapon_ref, TRUE)
-	INVOKE_ASYNC(weapon_ref, TYPE_PROC_REF(/atom/movable, forceMove), owner) // Just kinda shove it into the user
+	owner.transfer_item_to(weapon_ref, owner, force = TRUE, silent = TRUE)
 	owner.update_inv_l_hand()
 	owner.update_inv_r_hand()
 	playsound(get_turf(owner), 'sound/mecha/mechmove03.ogg', 25, TRUE, ignore_walls = FALSE)

code/modules/mob/inventory_procs.dm

@@ -164,7 +164,16 @@
 /**
  * Unequip `target` and drop it at our current location.
  *
- * Returns FALSE if the unequip failed, and `target` if it succeeded.
+ * Returns `FALSE` if the unequip failed, and `target` if it succeeded. Returns
+ * `FALSE` if there is no target to drop. If the caller cares about handling the
+ * resultant dropped object, they are responsible for ensuring that the thing
+ * actually exists. This is to ensure that the return value is meaningful and that
+ * a nonexistant item being unequipped and returning null is not interpreted as
+ * a failure.
+ *
+ * However, if you don't care about the return value, feel free to pass in possibly
+ * nonexistant objects, such as when dropping anything in a slot for a spell/virus
+ * that replaces existing clothing.
  */
 /mob/proc/drop_item_to_ground(obj/item/target, force = FALSE, silent = FALSE, drop_inventory = TRUE)
 	if(isnull(target))
@@ -179,13 +188,17 @@
 
 /**
  * Unequip `target` and relocate it to `destination`.
+ *
+ * Returns `FALSE` if the transfer failed for any reason, and `TRUE` if it succeeded.
  */
 /mob/proc/transfer_item_to(obj/item/target, atom/destination, force = FALSE, silent = TRUE)
 	return unequip_to(target, destination, force, silent, no_move = FALSE)
 
 /**
  * Unequip `target` without relocating it.
  *
+ * Returns `FALSE` if the transfer failed for any reason, and `TRUE` if it succeeded.
+ *
  * A destination cannot be specified; you must either `forceMove` or `qdel` it.
  * If you intend to `qdel` it immediately, it is not necessary to call this;
  * [/obj/item/proc/Destroy] will perform the necessary unequipping.