System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 2070 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 461.92

Blender Version
Broken: version: 2.93.0 Alpha, branch: master, commit date: 2021-04-02 21:26, hash: rB321eef6a0c0f
Worked: (newest version of Blender that worked as expected)

Short description of error
Attribute input fields on the front of a node group have an empty attribute lookup menu.

Exact steps for others to reproduce the error
Create a group node with an attribute input.
The attribute lookup popup will be empty.