Bug 21398: Make search field mandatory when adding to a basket from an existing record

Test plan:
- Create a basket
- Click the "Add to basket" button
- Click "Search" on the first line
=> Without this patch you get an ugly screen: https://snag.gy/U8X3ZK.jpg
=> With this patch applied you will not be able to submit without
filling the input in

QA note: Yes, we could handle that controller side as well, but much
more work.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit bf89e4e124)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 01588a68aa)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>

koha-tmpl/intranet-tmpl/prog/en/includes/acquisitions-add-to-basket.inc

@@ -5,7 +5,7 @@
         <li>
           <form action="/cgi-bin/koha/acqui/neworderbiblio.pl" method="post">
             <label>From an existing record:
-                <input type="text"  size="25" name="q" />
+                <input type="text"  size="25" name="q" required="required"/>
             </label>
             <input type="hidden" name="booksellerid" value="[% booksellerid %]" />
             <input type="hidden" name="basketno" value="[% basketno %]" />