libtuning: Handle cases, where no lsc tuning images are present

Make it clear that no lsc calibration was done by returning None instead
of a incomplete configuration.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

utils/tuning/libtuning/modules/lsc/rkisp1.py

@@ -107,6 +107,9 @@ class LSCRkISP1(LSC):
 
         output['sets'] = self._do_all_lsc(images)
 
+        if len(output['sets']) == 0:
+            return None
+
         # \todo Validate images from greyscale camera and force grescale mode
         # \todo Debug functionality