everytime I attempt to use the backpacks mod i keep on coming up with this on the web server
how can i fix this

Failed to run a 0.10 timer in 'Backpacks v3.1.0' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.Backpacks+Backpack.Get (System.UInt64 id) [0x0001d] in <94efd6b2b51a446a83897013c8714096>:0
  at Oxide.Plugins.Backpacks+<OpenBackpackConsoleCommand>c__AnonStorey4.<>m__0 () [0x00000] in <94efd6b2b51a446a83897013c8714096>:0
  at Oxide.Core.Libraries.Timer+TimerInstance.FireCallback () [0x00018] in <ac41dd3599754d448b8c218b34645820>

Better to post it here https://umod.org/plugins/backpacks

In mean while i can recommend you to wipe your data and config of backpacks