Correct close calls.

init.lua

@@ -38,7 +38,7 @@ local inp = io.open(fun_caves.world..'/fun_caves_data.txt','r')
 if inp then
 	local d = inp:read('*a')
 	fun_caves.db = minetest.deserialize(d)
-	inp.close()
+	inp:close()
 end
 if not fun_caves.db then
 	fun_caves.db = {}
@@ -160,7 +160,7 @@ minetest.register_on_shutdown(function()
 	if out then
 		print('Fun Caves: Saving database at shutdown')
 		out:write(minetest.serialize(fun_caves.db))
-		out.close()
+		out:close()
 	end
 end)