I just got this one as well:
Failed to call hook 'cmdChatClan' on plugin 'Clans v0.2.5' (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Game.Rust.Libraries.Player.Message (BasePlayer player, System.String message, System.String prefix, System.UInt64 userId, System.Object[] args) [0x00038] in <2c1077bb44b848bdbd608979e0b54808>:0
at Oxide.Game.Rust.Libraries.Covalence.RustPlayer.Message (System.String message, System.String prefix, System.Object[] args) [0x00000] in <2c1077bb44b848bdbd608979e0b54808>:0
at Oxide.Game.Rust.Libraries.Covalence.RustPlayer.Reply (System.String message, System.String prefix, System.Object[] args) [0x0000f] in <2c1077bb44b848bdbd608979e0b54808>:0
at Oxide.Game.Rust.Libraries.Covalence.RustPlayer.Reply (System.String message) [0x00008] in <2c1077bb44b848bdbd608979e0b54808>:0
at Oxide.Plugins.Clans+Clan.InvitePlayer (Oxide.Core.Libraries.Covalence.IPlayer inviter, Oxide.Core.Libraries.Covalence.IPlayer invitee) [0x0016e] in <8c1934aa37ce4638a4fc2579fb67bb47>:0
at Oxide.Plugins.Clans.InvitePlayer (Oxide.Core.Libraries.Covalence.IPlayer inviter, Oxide.Core.Libraries.Covalence.IPlayer invitee) [0x00079] in <8c1934aa37ce4638a4fc2579fb67bb47>:0
at Oxide.Plugins.Clans.cmdChatClan (Oxide.Core.Libraries.Covalence.IPlayer player, System.String command, System.String[] args) [0x0036e] in <8c1934aa37ce4638a4fc2579fb67bb47>:0
at Oxide.Plugins.Clans.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00727] in <8c1934aa37ce4638a4fc2579fb67bb47>:0
at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <b6af59acae274e5a94fb209dfc179b8f>:0
at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <0d3ec4223e1545f9b3666f4f73517a10>:0
at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <0d3ec4223e1545f9b3666f4f73517a10>:0