Merge branch 'bugfix/always-return-correct-nonzeroes' into 'master'

[bugfix] ensure nonzeroes always return the number of nonzero entries

Closes #28 (closed)

See merge request !127 (merged)

(cherry picked from commit 9a7e58fe)

572d972c [bugfix] ensure nonzeroes always return the number of nonzero entries

enabled an automatic merge when the pipeline for 7a021eb9 succeeds

mentioned in commit 661ba782

merged