Changes in ggplot break boxplot in fastqc_summary.R

In particular this plot:

https://git.mpi-cbg.de/bioinfo/ngs_tools/blob/master/common/fastqc_summary.R#L187

with the error:

Error: Can't draw more than one boxplot per group. Did you forget aes(group = ...)?

This has been noticed before:

https://stackoverflow.com/questions/57192727/getting-an-error-that-ggplot2-3-2-0-cant-draw-more-than-one-boxplot-per-group