Cannot place solar roofing

[ravage382]

Running the steam workshop build of this git. When trying to place solar roof, I click start and end point for the zone. The second click that should start the building ends up deselecting the zone. Roof is never built.
Turning on development mode gives: "Root level exception in OnGUI(): System.NullReferenceException: Object reference not set to an instance of an object
at (wrapper dynamic-method) Verse.ThingMaker.DMD<DMD<MakeThing_Patch1>?-1253556864::MakeThing_Patch1>(Verse.ThingDef,Verse.ThingDef)
at (wrapper dynamic-method) RimWorld.GenConstruct.DMD<DMD<PlaceBlueprintForBuild_Patch3>?-1366774912::PlaceBlueprintForBuild_Patch3>(Verse.BuildableDef,Verse.IntVec3,Verse.Map,Verse.Rot4,RimWorld.Faction,Verse.ThingDef)
at ExpandedRoofing.Designator_BuildCustomRoof.DesignateSingleCell (Verse.IntVec3 c) [0x000e4] in :0
at Verse.Designator.DesignateMultiCell (System.Collections.Generic.IEnumerable`1[T] cells) [0x00041] in <36108d57f84d49cabdae818c2a53fc38>:0
at Verse.DesignatorManager.ProcessInputEvents () [0x0012c] in <36108d57f84d49cabdae818c2a53fc38>:0
at RimWorld.MapInterface.HandleMapClicks () [0x0000f] in <36108d57f84d49cabdae818c2a53fc38>:0
at RimWorld.UIRoot_Play.UIRootOnGUI () [0x00089] in <36108d57f84d49cabdae818c2a53fc38>:0
at Verse.Root.OnGUI () [0x0003d] in <36108d57f84d49cabdae818c2a53fc38>:0
Verse.Log:Error(String, Boolean)
Verse.Root:OnGUI()
"