The isoform switching summary has an off-by-one error when there are no results to report. The ID lists, instead of being empty vectors, contain a NA value. As a result, the tallies report values of 1 instead of 0. When there are results to report, the NAs and the off-by-one error do not apply.

This is likely a data.table subsetting error. When nothing matches the subset criteria, data.table returns a row of NA. I need to catch this.

A similar issue used to happen with the DTU summary, so that should serve as a template for the solution here too.