Fix null referent handling

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased Changes
 * Fixed the Rojo plugin attempted to write the non-scriptable properties `Instance.SourceAssetId` and `HttpServer.HttpEnabled`.
+* Fixed the Rojo plugin's handling of null referents.
 
 ## [6.0.0 Release Candidate 2](https://github.com/rojo-rbx/rojo/releases/tag/v6.0.0-rc.2) (November 19, 2020)
 * Fixed crash when malformed CSV files are put into a project. ([#310](https://github.com/rojo-rbx/rojo/issues/310))

plugin/src/Reconciler/decodeValue.lua

@@ -9,6 +9,10 @@ local Error = require(script.Parent.Error)
 local function decodeValue(virtualValue, instanceMap)
 	-- Refs are represented as IDs in the same space that Rojo's protocol uses.
 	if virtualValue.Type == "Ref" then
+		if virtualValue.Value == nil then
+			return true, nil
+		end
+
 		local instance = instanceMap.fromIds[virtualValue.Value]
 
 		if instance ~= nil then

plugin/src/Reconciler/reify.lua

@@ -136,15 +136,21 @@ function applyDeferredRefs(instanceMap, deferredRefs, unappliedPatch)
 	end
 
 	for _, entry in ipairs(deferredRefs) do
-		local targetInstance = instanceMap.fromIds[entry.virtualValue.Value]
+		local virtualValue = entry.virtualValue
+
+		if virtualValue.Value == nil then
+			continue
+		end
+
+		local targetInstance = instanceMap.fromIds[virtualValue.Value]
 		if targetInstance == nil then
-			markFailed(entry.id, entry.propertyName, entry.virtualValue)
+			markFailed(entry.id, entry.propertyName, virtualValue)
 			continue
 		end
 
 		local ok = setProperty(entry.instance, entry.propertyName, targetInstance)
 		if not ok then
-			markFailed(entry.id, entry.propertyName, entry.virtualValue)
+			markFailed(entry.id, entry.propertyName, virtualValue)
 		end
 	end
 end