Fix NPE for parallel lines preview with intersect plane/quadric tool

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24161 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Intersect plane/limited quadric (part 1) : outline (double line)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24162 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e