histogram: handle non-list members in tester_is_valid_histogram/1
histogram: handle non-list members in tester_is_valid_histogram/1

check whether Data is a list before calling length(Data)

scalaris-team/scalaris,jvf/scalaris,jvf/scalaris,scalaris-team/scalaris,jvf/scalaris,jvf/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,jvf/scalaris,jvf/scalaris,jvf/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris