show exportDialog if upload to geogebratube ends up in an error

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36767 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
minor bugfixes for menu (web)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36768 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e