[BUGFIX] Warning in SearchController

$this->sWArr is not defined SearchController.
Fix this to use the correct $this->searchWords variable.

Change-Id: Iba888f1a47dcc0952ffbbb1e3bb4413435c2a95e
Resolves: #59277
Releases: 6.2, 6.1
Reviewed-on: https://review.typo3.org/30587
Reviewed-by: Markus Klein
Tested-by: Markus Klein