Bug 37628: (follow-up) Remove get_opac_news_by_id

Bug 37628: (follow-up) Remove get_opac_news_by_id

Keep the same behaviour, but wondering why we don't return 'content'
when there is no match.

ie.
+    is( $additional_contents, undef );
should certainly be
+    is( $additional_contents->{content}->count, 0 );

WNC amended patch - tidied

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>