Ticket 93. When BoxPlot is run with only one group, the ANOVA statistical model will not work and generates a user-unfriendly error. This has now been caught to return a more understandable error.
Changed way of testing whether there are plenty of levels in the data to one that actually works. Tested.
Merge pull request #20 from thehyve/bug/93BoxPlotInsufficientLevelsErrorFeedback

Bug/93 box plot insufficient levels error feedback