decebals/wicket-pivot — pull request #2 by rototor (2013-09-25 15:41:46+00:00)
Title: Allow null values in the ROW/COLUMN values. 

The user might select some nullable numeric fields for grouping (which doesn't really make sense for
grouping) and should not see a NullPointerException in this case.

null-values are treated as equal and sorted first.