Missing group keyword in call to test_group (#39)
Missing group keyword in call to test_group (#39)

In the check_equipartiton function the group keyword for calls to test_group with randomised or user-defined groups was not specified, therefore the group in "test_group" defaulted to None effectively giving the same, system wide, equipartition analysis for all groups. 
I added the keyword and added a check in test_group to catch DoFs with zero DoFs, because passing these DoFs resulted in errors in the trajectory analysis of the pymbar module.

Co-authored-by: MonophoniqueK <fa3289599bf0bdefcb0802e468138b0dbfba5cc7@users.noreply.github.com>
Co-authored-by: Pascal Merz <5e62c294fa32f9f14994f394f710ce92af3de959@me.com>
shirtsgroup/physical-validation