Someone please help me fix this error

help i am making a world and when i go to publish it it shos this even though im using sdk 3.0 and am using version VRCSDK3-WORLD-2021. NullReferenceException: Object reference not set to an instance of an object
VRCSDK2.RuntimeWorldCreation.Start () (at Assets/VRCSDK/Dependencies/VRChat/Scripts/RuntimeWorldCreation.cs:82)

Did you import both VRCSDK2 and VRCSDK3 to project?

What ulti said,
SDK 2 and SDK 3 aren’t compatible.

If you’re migrating an sdk2 world to sdk3 you’ll have to remove the vrcsdk folder entirely before importing sdk3

Do you have an Udon script on something with a public variable on it that is not set, maybe?

Check over any Udon Behaviors and make sure there aren’t any with an empty field for something being referenced in the script.

that’s a different error, unfilled variables will just halt the udon execution instead of throwing an sdk2 error