Make sure delete does not fail when you try to delete already deleted object

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@38158 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Image tool working at least with local files

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@38159 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e