Bug 11183: get rid of some log noise from the OPAC

Bug 11183: get rid of some log noise from the OPAC

To test in OPAC:
* With the OPAC System Preference EnableOpacSearchHistory set
  to Keep, a simple search triggers the warning patched on
  line 626 of opac-search.pl
* Selecting a search result item with no Collection Code
  set triggers the warning patched on line 576 of opac-detail.pl
* Have an item with Collection Code. Check that the Collection
  Code shows.
* Collection Code is set by editing an item in the staff client
  (952$8)

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit ec206d18980b2438cfe3da9e89455eda319dd8d7)
Signed-off-by: Fridolin SOMERS <fridolin.somers@biblibre.com>