Message before logging Forge1.12.2 (Missing Registries: minecraft:dataserializers).

Though it has never stopped anyone from entering my modded server (once one press the yes button) this message keeps showing up after clicking to connect. It started when I exchanged the world file. I'm getting a little worried since its content actually alerts me it might cause issues. Is there anyone who knows why this is happening and how to make it stop? heeelp pleease (Even if it represents no threatening, it is annoying).

you're not wrong, but I've already stated what you said. I'm asking for help regardless of it being ignorable