accept only avatar_url beginning with //
accept only avatar_url beginning with //

Signed-off-by: Benoît Sibaud <f9cfa8e32c72b5142bc42dbc6a82673f15ff05a0@linuxfr.org>

cykl/linuxfr.org,linuxfrorg/linuxfr.org,cykl/linuxfr.org,linuxfrorg/linuxfr.org,linuxfrorg/linuxfr.org,linuxfrorg/linuxfr.org