Unloaded plugin Fishing v1.4.10 by Colon Blow
Loaded plugin Fishing v1.4.10 by Colon Blow
Failed to call hook 'OnPlayerAttack' on plugin 'Fishing v1.4.10' (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.Fishing.ProcessSpearFish (BasePlayer attacker, HitInfo hitInfo) [0x0000a] in <0d61f46c30314a7285cac05372f754f4>:0

did the error only happen the one time after reloading the plugin? 

that could be normal, if player was in middle of "attacking" to fish and the plugin reloaded.

or does it keep happening?