support null values in cut strings via __null__ value; support empty string values as well, e.g. attr:unpaid,direct, is different than attr:unpaid,direct
support null values in cut strings via __null__ value; support empty
string values as well, e.g. attr:unpaid,direct, is different than
attr:unpaid,direct

pombredanne/cubes,pombredanne/cubes,ubreddy/cubes,she11c0de/cubes,noyeitan/cubes,noyeitan/cubes,jell0720/cubes,zejn/cubes,cesarmarinhorj/cubes,cesarmarinhorj/cubes,zejn/cubes,jell0720/cubes,cesarmarinhorj/cubes,jell0720/cubes,ubreddy/cubes,noyeitan/cubes,she11c0de/cubes,she11c0de/cubes,zejn/cubes,pombredanne/cubes,ubreddy/cubes