Fix error for no objects by type checking

inference/face_detector.py

@@ -96,7 +96,7 @@ class StatRetinaFaceDetector(FaceDetector):
     def detect_crops(self, img, *args, **kwargs):
         faces = RetinaFace.detect_faces(img, model=self.model)
         crops = []
-        if len(faces) == 0:
+        if isinstance(faces, tuple):
             faces = {}
         for name, face in faces.items():
             x1, y1, x2, y2 = face['facial_area']