Is this normal or is it something that should be fixed
06/19 15:27:55 | Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at BuildingBlock.SetGrade (BuildingGrade+Enum iGrade) [0x00000] in <ac2dcd605fa04bcbb834583fa71ad870>:0
at BuildingBlock.ChangeGrade (BuildingGrade+Enum targetGrade, System.Boolean playEffect, System.Boolean updateSkin) [0x00000] in <ac2dcd605fa04bcbb834583fa71ad870>:0
at BuildingBlock.ChangeGradeAndSkin (BuildingGrade+Enum targetGrade, System.UInt64 skin, System.Boolean playEffect, System.Boolean updateSkin) [0x0000d] in <ac2dcd605fa04bcbb834583fa71ad870>:0
at Oxide.Plugins.BuildingSkins+<OnStructureUpgrade>c__AnonStorey3.<>m__0 () [0x00000] in <d4c385d3e1754045af41a3564596f95d>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <157a94ee66ab4a7991faecd1eb84be3b>:0