Exclude samples from bismark2summary if they have no methylation calls in some context

[FelixKrueger]

In some single-cell applications we have situations where close to none (or in fact no reads) make it to the methylation extraction stage. Missing values, or e.g. 0 calls methylated and 0 calls unmethylated in any context cause the plot in the HTML file to be empty.

Can we take a look if we can exclude such reads entirely from the HTML report?