Hi, for prefect 0.15.13 i'm getting this error when trying to set up a mapped task run

Traceback (most recent call last):
  File "/home/wwolfe-mcguire/.conda/envs/dev_env/lib/python3.9/site-packages/prefect/engine/runner.py", line 48, in inner
    new_state = method(self, state, *args, **kwargs)
  File "/home/wwolfe-mcguire/.conda/envs/dev_env/lib/python3.9/site-packages/prefect/engine/flow_runner.py", line 569, in get_flow_run_state
    executors.prepare_upstream_states_for_mapping(
  File "/home/wwolfe-mcguire/.conda/envs/dev_env/lib/python3.9/site-packages/prefect/utilities/executors.py", line 681, in prepare_upstream_states_for_mapping
    value = upstream_state.result[i]
KeyError: 0
[2022-09-26 15:42:45+0000] ERROR - prefect.ml-graph-energy | Unexpected error occured in FlowRunner: KeyError(0)

I wasn't able to find other examples of a similar error online and was hoping someone could give me some hints about how to start debugging this. thanks

Hey @William Wolfe-McGuire could you provide some additional context around the flow you're running, i.e. a Minimum reproducible example of what you're seeing occur. a key value error here is likely going to be very contextual rather than being a specific prefect issue