I have the same problem.

(18:48:39) | Failed to call hook 'OnEventPlayerDeath' on plugin 'ArenaDeathmatch v1.2.22' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.ArenaDeathmatch.OnEventPlayerDeath (BasePlayer victim, HitInfo hitinfo) [0x0000b] in <73c0f80cb86d4366a480ff6585a47125>:0 
  at Oxide.Plugins.ArenaDeathmatch.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x003c0] in <73c0f80cb86d4366a480ff6585a47125>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <3e46d2a997e94a3cb08cf065508cd483>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <1fe782f4b27a43ae85d29ebb2d56c007>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <1fe782f4b27a43ae85d29ebb2d56c007>:0

(18:48:39) | Calling hook canRedeemKit resulted in a conflict between the following plugins: ZoneManager - You may not redeem a kit inside this area (String), EventManager (You may not redeem a kit in the arena (String))