fix: underflow in container slot search for non-stackables

src/creatures/players/player.cpp

@@ -62,7 +62,7 @@
 
 MuteCountMap Player::muteCountMap;
 
 Player::Player(std::shared_ptr<ProtocolGame> p) :
 	lastPing(OTSYS_TIME()),
 	lastPong(lastPing),
 	inbox(std::make_shared<Inbox>(ITEM_INBOX)),
@@ -4604,16 +4604,21 @@
 		while (i < containers.size()) {
 			std::shared_ptr<Container> tmpContainer = containers[i++];
 			if (!autoStack || !isStackable) {
-				// we need to find first empty container as fast as we can for non-stackable items
-				uint32_t n = tmpContainer->capacity() - tmpContainer->size();
-				while (n) {
-					if (tmpContainer->queryAdd(tmpContainer->capacity() - n, item, item->getItemCount(), flags) == RETURNVALUE_NOERROR) {
-						index = tmpContainer->capacity() - n;
+				const uint32_t containerCapacity = tmpContainer->capacity();
+				const uint32_t containerSize = tmpContainer->size();
+
+				// Avoid underflow in the loop below
+				if (containerSize >= containerCapacity) {
+					continue;
+				}
+
+				for (uint32_t pos = 0; pos < containerCapacity; ++pos) {
+					auto rv = tmpContainer->queryAdd(pos, item, item->getItemCount(), flags);
+					if (rv == RETURNVALUE_NOERROR) {
+						index = pos;
 						destItem = nullptr;
 						return tmpContainer;
 					}
-
-					n--;
 				}
 
 				for (const auto &tmpContainerItem : tmpContainer->getItemList()) {
@@ -8884,7 +8889,7 @@
 }
 
 void Player::stowItem(const std::shared_ptr<Item> &item, uint32_t count, bool allItems) {
 	if (!item || !item->isItemStorable() && item->getID() != ITEM_GOLD_POUCH) {
 		sendCancelMessage("This item cannot be stowed here.");
 		return;
 	}