What is the interaction between mold earth and create bonfire?

If I cast create bonfire in a 5 foot unoccupied space. Then next round cast mold earth to excavate that same area creating a 5 foot pit underneath the fire; Does the bonfire fall or stay at ground level?

This came up in game. The bonfire is magically created and does not need to burn fuel. So it could float. But does it? Is there a precident?