Handle cases when face is not detected

bob/ip/dlib/DlibLandmarkExtraction.py

@@ -52,10 +52,12 @@ class DlibLandmarkExtraction(object):
 
         # Detecting the face if the bounding box is not passed
         if bb is None:
-            bb = bounding_box_2_rectangle(self.face_detector.detect_single_face(image)[0])
+            bb = self.face_detector.detect_single_face(image)
 
             if bb is None:
                 return None
+
+            bb = bounding_box_2_rectangle(bb[0])
         else:
             bb = bounding_box_2_rectangle(bb)