Harden deserialize workaround against unexpected input

Otherwise it will stop working entirely soon when the
serialization inside Minetest is reworked.
This allows it to work at least in the cases where the original
bug (LuaJIT register limit) doesn't apply.

worldedit/serialization.lua

@@ -114,12 +114,15 @@ function worldedit.serialize(pos1, pos2)
 	return LATEST_SERIALIZATION_HEADER .. result, count
 end
 
--- Contains code based on [table.save/table.load](http://lua-users.org/wiki/SaveTableToFile)
--- by ChillCode, available under the MIT license.
 local function deserialize_workaround(content)
 	local nodes
 	if not minetest.global_exists("jit") then
 		nodes = minetest.deserialize(content, true)
+	elseif not content:match("^%s*return%s*{") then
+		-- The data doesn't look like we expect it to so we can't apply the workaround.
+		-- hope for the best
+		minetest.log("warning", "WorldEdit: deserializing data but can't apply LuaJIT workaround")
+		nodes = minetest.deserialize(content, true)
 	else
 		-- XXX: This is a filthy hack that works surprisingly well
 		-- in LuaJIT, `minetest.deserialize` will fail due to the register limit
@@ -130,7 +133,7 @@ local function deserialize_workaround(content)
 		local startpos, startpos1 = 1, 1
 		local endpos
 		while true do -- go through each individual node entry (except the last)
-			startpos, endpos = escaped:find("},%s*{", startpos)
+			startpos, endpos = escaped:find("}%s*,%s*{", startpos)
 			if not startpos then
 				break
 			end