Submitting list instead of float as trial does not raise an error and make Bender crash

Bender clients allow the following syntax as a valid result for a given trial:
`
results = {"metric_a": [0.5,0.6,0.7]}
` 
` 
 bender.create_trial(
        hyperparameters=suggestion,
        results=results
  )
` 
The creation of the trial make the web-client crash and getting new suggestion for the algo impossible.
