QMimeDatabase: fix mimeTypeForUrl for mailto URLs

The "path" of a mailto URL isn't a file, so we shouldn't try to do
glob-based matching. I was getting application/x-ms-dos-executable
for a .com domain and application/x-perl for a .pl domain...

Change-Id: Ifc346c3bba83ba1a8476db3202492f4c2e4d52bb
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>