I am now getting this error message in the server console after the update. hope it helps

08:49 [Error] Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.PlaguedNPCs+<OnEntitySpawned>c__AnonStorey0.<>m__0 () [0x00056] in <b88d544ed69a49038ff0170467785af8>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <99d545163fdd4d57a562df7989f2ca0a>:0

Should be fixed for the next version, thanks for the report!