[3.0] Fix search issues

[sbulen]

Fixes #9147

Unwrapping this in layers... First issue was easy, looks to be just a copy/paste error.

Will keep flailing away until it works.

The things I'll do to avoid working on taxes...

[sbulen]

Next layer of the problem is harder, still can't find a fix. On screen, it displays:

implode(): If argument # 1 ($separator) is of type string, argument # 2 ($array) must be of type array, null given

In the error log it displays the above and also some undefined array key issues, e.g.:

2: Undefined array key "boards_check_all", Search.template.php, line 166