bugfix: SigmaXX[{1, 2, 3}, {2, 4, 8}] should give 90

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@22886 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Fix for #2949

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@22887 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e