System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 3070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 462.59

Blender Version
Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-05-22 04:53, hash: rBf7b22fc3d271
Worked: Latest 2.93 nightly build (1a69d491e57c)

Introduced with rBb084b57fbf6d: Geometry Nodes: new geometry nodes evaluator

Short description of error
Plugging an empty string output from a node group into an Attribute Remove input prints an error in the console. No add-on enabled.
It doesn't hard crash but seems to randomly make the file unstable, a crash eventually happens afterwards doing seemingly unrelated things.
I've narrowed it down to a combination of nodes :

Inside the node group :

Exact steps for others to reproduce the error
Brand new file :

Create a Cube
Add a GN modifier
Plug Attribute Remove node between input and output nodes
Plug string node into the Attribute Remove second input
Select the string node
CTRL G to group
Delete the string node

Console prints error :

Code marked as unreachable has been executed. Please report this as a bug.
Error found at C:\Users\blender\git\blender-vdev\blender.git\source\blender\modifiers\intern\MOD_nodes_evaluator.cc:1475 in operator ().

See Blend file and error logs attached