Fixed an exception thrown when buying from player stock

Fix issue where malformed stock could shift following shop items

Server/src/test/kotlin/ShopTests.kt

@@ -4,6 +4,8 @@ import org.junit.Assert
 import org.junit.jupiter.api.Assertions
 import org.junit.jupiter.api.Test
 import rs09.game.content.global.shops.Shop
+import rs09.game.content.global.shops.Shops
+import rs09.game.system.config.ShopParser
 
 class ShopTests {
     val testPlayer = TestUtils.getMockPlayer("test")
@@ -114,4 +116,29 @@ class ShopTests {
             general.restock()
         }
     }
+
+    @Test fun playerStockShouldNeverBeNull() {
+        Assertions.assertNotNull(general.playerStock)
+    }
+
+    @Test fun shouldAllowBuyingFromPlayerStockOnMultipleRows() {
+        for(i in 0 until 100) {
+            general.playerStock.add(Item(i + 3100, 1)) //make sure we populate several rows of items
+        }
+        testPlayer.inventory.add(Item(995, 100000))
+        testPlayer.setAttribute("shop-cont", general.getContainer(testPlayer))
+        testPlayer.setAttribute("shop-main", false)
+        var status: Shop.TransactionStatus = Shop.TransactionStatus.Success()
+        Assertions.assertDoesNotThrow({
+            status = general.buy(testPlayer, 36, 1)
+        }, "Error selling to shop: ${general.playerStock}")
+        Assertions.assertEquals(true, status is Shop.TransactionStatus.Success)
+    }
+
+    @Test fun invalidStockJsonShouldNotCauseItemShift() {
+        val invalidJson = "{1277,10,100}-{1277,10,100}-{1279,10,100}"
+        val stock = Shops.parseStock(invalidJson, -1)
+        Assertions.assertEquals(2, stock.size)
+        Assertions.assertEquals(20, stock[0].amount)
+    }
 }