percent_strong outputs nan when no replicates are present

[gwaybio]

When no replicates are present, denom = 0 and we receive the following error:

/home/ubuntu/efs/Periscope_Calico/workspace/software/Periscope_Calico/miniconda3/envs/pooled-cell-painting/lib/python3.7/site-packages/cytominer_eval/operations/percent_strong.py:50: RuntimeWarning: invalid value encountered in long_scalars
  ).sum() / denom

We should add an AssertionError when denom = 0 and provide an error message that "no replicate groups identified".

The line is

cytominer-eval/cytominer_eval/operations/percent_strong.py

Lines 45 to 50 in 56bd9e5

	replicate_df = similarity_melted_df.query("group_replicate")
	denom = replicate_df.shape[0]
	percent_strong = (
	replicate_df.similarity_metric > non_replicate_quantile
	).sum() / denom