#4371 defensive code

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36323 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
SVG images working (web & desktop) #4530

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36324 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e