Simplify `areas:save()`

internal.lua

@@ -4,26 +4,14 @@ function areas:player_exists(name)
 	return minetest.get_auth_handler().get_auth(name) ~= nil
 end
 
-local safe_file_write = minetest.safe_file_write
-if safe_file_write == nil then
-	function safe_file_write(path, content)
-		local file, err = io.open(path, "w")
-		if err then
-			return err
-		end
-		file:write(content)
-		file:close()
-	end
-end
-
 -- Save the areas table to a file
 function areas:save()
-	local datastr = minetest.write_json(self.areas)
+	local datastr = minetest.write_json(self.areas, true)
 	if not datastr then
 		minetest.log("error", "[areas] Failed to serialize area data!")
 		return
 	end
-	return safe_file_write(self.config.filename, datastr)
+	return minetest.safe_file_write(self.config.filename, datastr)
 end
 
 -- Load the areas table from the save file