Fixed possible NPE

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23563 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Fixed warnings

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23564 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e