toolbar substitute dynamic && null check if there are any variables at all #3614

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@28415 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#3612 fix

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@28416 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e