Failed to call hook 'OnDispenserBonusReceived'

Hi! There are a lot of errors when starting an Gold Rush event.

[Oxide] 09:52 [Error] Failed to call hook 'OnDispenserBonusReceived' on plugin 'MultiEventsGoldRush v1.0.0' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.MultiEventsGoldRush+Configuration+<>c__DisplayClass5_0.<GetPermissionMultiplier>b__0 (System.Collections.Generic.KeyValuePair`2[TKey,TValue] check) [0x00012] in <ad747f7854344f23a901d109ccd24a01>:0
  at System.Linq.Enumerable+WhereEnumerableIterator`1[TSource].MoveNext () [0x00037] in <a314714511a14f84b853c03efd8682b8>:0
  at System.Linq.Enumerable.Aggregate[TSource,TAccumulate] (System.Collections.Generic.IEnumerable`1[T] source, TAccumulate seed, System.Func`3[T1,T2,TResult] func) [0x00037] in <a314714511a14f84b853c03efd8682b8>:0
  at Oxide.Plugins.MultiEventsGoldRush+Configuration.GetPermissionMultiplier (BasePlayer player) [0x00024] in <ad747f7854344f23a901d109ccd24a01>:0
  at Oxide.Plugins.MultiEventsGoldRush.RollItems (BasePlayer player, System.Collections.Generic.List`1[T] items) [0x00011] in <ad747f7854344f23a901d109ccd24a01>:0
  at Oxide.Plugins.MultiEventsGoldRush.OnDispenserBonusReceived (ResourceDispenser dispenser, BasePlayer player, Item item) [0x00048] in <ad747f7854344f23a901d109ccd24a01>:0
  at Oxide.Plugins.MultiEventsGoldRush.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x000b8] in <ad747f7854344f23a901d109ccd24a01>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <42f9bedc659b4f4786eb778d3cd58968>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000de] in <112d89ea5d3348c8b949af0ab1a866d2>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <112d89ea5d3348c8b949af0ab1a866d2>:0

Hello! Please, send me your config 

{
  "Work with Notify?": true,
  "Event Duration": 600,
  "Ore items": [
    {
      "Type": "Item",
      "Command (%steamid%)": "",
      "Kit": "",
      "Plugin": {
        "Hook": null,
        "Plugin Name": null,
        "Amount": 0
      },
      "Item": {
        "DisplayName (empty - default)": "",
        "ShortName": "wood",
        "Skin": 0,
        "Amount min": 3500,
        "Amount max": 4500
      },
      "Chance": 50.0
    },
    {
      "Type": "Item",
      "Command (%steamid%)": "",
      "Kit": "",
      "Plugin": {
        "Hook": null,
        "Plugin Name": null,
        "Amount": 0
      },
      "Item": {
        "DisplayName (empty - default)": "",
        "ShortName": "stones",
        "Skin": 0,
        "Amount min": 3500,
        "Amount max": 4500
      },
      "Chance": 20.0
    },
    {
      "Type": "Item",
      "Command (%steamid%)": "",
      "Kit": "",
      "Plugin": {
        "Hook": null,
        "Plugin Name": null,
        "Amount": 0
      },
      "Item": {
        "DisplayName (empty - default)": "",
        "ShortName": "scrap",
        "Skin": 0,
        "Amount min": 100,
        "Amount max": 200
      },
      "Chance": 20.0
    }
  ],
  "Tree items": [
    {
      "Type": "Item",
      "Command (%steamid%)": "",
      "Kit": "",
      "Plugin": {
        "Hook": null,
        "Plugin Name": null,
        "Amount": 0
      },
      "Item": {
        "DisplayName (empty - default)": "",
        "ShortName": "wood",
        "Skin": 0,
        "Amount min": 3500,
        "Amount max": 4500
      },
      "Chance": 30.0
    },
    {
      "Type": "Item",
      "Command (%steamid%)": "",
      "Kit": "",
      "Plugin": {
        "Hook": null,
        "Plugin Name": null,
        "Amount": 0
      },
      "Item": {
        "DisplayName (empty - default)": "",
        "ShortName": "stones",
        "Skin": 0,
        "Amount min": 3500,
        "Amount max": 4500
      },
      "Chance": 20.0
    },
    {
      "Type": "Item",
      "Command (%steamid%)": "",
      "Kit": "",
      "Plugin": {
        "Hook": null,
        "Plugin Name": null,
        "Amount": 0
      },
      "Item": {
        "DisplayName (empty - default)": "",
        "ShortName": "scrap",
        "Skin": 0,
        "Amount min": 100,
        "Amount max": 200
      },
      "Chance": 30.0
    }
  ],
  "Permissions Multiplier chane [item chance * perm chance]": {
    "MultiEventsGoldRush.vip": 2.0
  }
}

Thank, I will check it