My inventory opens and closes on left mouse click when i don't want it to.

So i was following a tutorial and i made an inventory that opens and closes when i press i, the issue is it also opens and closes whenever i left mouse click and i don't know why.

Here's the code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Inventory : MonoBehaviour {
     public int SlotsX, SlotsY;
     public GUISkin skin;
     public List<Item> inventory = new List<Item>();
     public List<Item> slots = new List<Item>();
     private bool showInventory;
     private ItemDatabase database;
     private bool showTooltip;
     private string tooltip;
 
     private bool draggingitem;
     private Item draggedItem;
 
 
     // Use this for initialization
     void Start () {
         for (int i = 0; i < (SlotsX * SlotsY); i++)
         {
             slots.Add(new Item());
             inventory.Add (new Item ());
         }
         database = GameObject.FindGameObjectWithTag("Item Database").GetComponent<ItemDatabase>();
         AddItem(1);
         AddItem(0); 
         RemoveItem (1);
 
         print (InventoryContains (1));
     }
 
     void Update()
     {
         if (Input.GetButtonDown ("Inventory")) 
         {
             showInventory = !showInventory;
         }
     }
 
     void  OnGUI ()
     {
         tooltip = "";
         GUI.skin = skin;
         if (showInventory)
         {
             DrawInventory ();
             if (showTooltip) 
                 GUI.Box (new Rect (Event.current.mousePosition.x + 15f, Event.current.mousePosition.y, 200, 200), tooltip, skin.GetStyle("Tooltip"));
         
         }
         if (draggingitem)
         {
             GUI.DrawTexture(new Rect(Event.current.mousePosition.x, Event.current.mousePosition.y, 50, 50), draggedItem.itemIcon);
         }
 
     }
     void DrawInventory()
     {
         Event e = Event.current;
         int i = 0;
         for (int y = 0; y < SlotsY; y++) 
         {
             
             for (int x = 0; x < SlotsX; x++)
             {
                 Rect slotRect = new Rect (x * 110, y * 110, 100, 100);
                 GUI.Box (slotRect, "", skin.GetStyle("Slot"));
                 slots[i] = inventory[i];
 
                 if(slots[i].itemName != null)
                 {
                     GUI.DrawTexture(slotRect, slots[i].itemIcon);
                     if (slotRect.Contains(e.mousePosition)) 
                     {
                         tooltip = CreateTooltip (inventory[i]);
                         showTooltip = true;
                         if (e.button == 0 && e.type == EventType.MouseDrag)
                         {
                             draggingitem = true;
                             draggedItem = slots [i];
                         }
                     }
                 }
                 if (tooltip == "")
                 {
                     showTooltip = false;
                 }
                 i++;
             }
         }
     }
     string CreateTooltip(Item item)
     {
         tooltip = "<color=#ffffff>" + item.itemName + "</color>\n\n" +item.itemDesc;
         return tooltip;
     }
 
     void RemoveItem(int id)
     {
         for(int i = 0; i < inventory.Count; i++)
         {
             if(inventory[i].itemID == id)
             {
                 inventory [i] = new Item();
                 break;
             }
         }
     }
 
     void AddItem(int id)
     {
         for (int i = 0; i < inventory.Count; i++) 
         {
             if (inventory [i].itemName == null) 
             {    
                 for (int j = 0; j < database.items.Count; j++)
                 {
                     if (database.items [j].itemID == id) 
                     {
                         inventory [i] = database.items [j];
                     }
                 }    
                 break;        
             }
         }
     }
 
     bool InventoryContains(int id)
     {
         bool result = false;
         for (int i = 0; i < inventory.Count; i++) 
         {
             result = inventory [i].itemID == id;
             if (result)
             {
                 break;
             }
 
         }
         return result;
     }
 }

I have no idea which part of the code is causing this, i just assumed Unity is assigning left mouse click to the function by default because it's not used currently but now i came to the point where it actually is used for something else and the problem persists.