Error cleanly when no output requested using .materialize

[skrawcz]

If no output is requested using .materialize() we don't error at all.

Current behavior

It gets stuck in an infinite loop.

Steps to replicate behavior

This recreates the behavior -- there is no output requested.

# test.py
from hamilton import driver
from hamilton.plugins import h_experiments
from hamilton.io.materialization import to, from_

def connect(a:dict) -> str:
    print('connect')
    print(a)
    return 'connect'

if __name__ == "__main__":
    import test

    tracker_hook = h_experiments.ExperimentTracker(
        experiment_name='exp',
        base_directory='.',
    )


    dr = (
        driver.Builder()
        .with_modules(test)
        .enable_dynamic_execution(allow_experimental_mode=True)
        # .with_execution_manager(execution_manager)
        .with_adapters(tracker_hook)
        .build()
    )
    materilizers = [
        from_.pickle(path='./data.pickle', target='a'),
    ]
    dr.materialize(*materilizers)

Library & System Information

Latest hamilton, mac.

Expected behavior

It errors out.

Additional context