[Mapserver-inspire] patch to comply with wms 1.3.0 §7.3.3.6

[Martin Kofahl]

Hi Stephan,
during wms/inspire conformity tests, there was a failure when do a GetMap far away from the map extent. Instead of returning an empty, single colored image, a copyright text configures in map files is still visible. According to the wms spec, this is not allowed.

I filed a ticket #4126. Could you please discuss/review it an possibly consider transfering the patch attached to #4126 to your mapserver-inspire sandbox, because MapServer would otherwise fail complex inspire testsuites?

Kind regards,
Martin