fixed numpy error

inference.py

@@ -204,7 +204,8 @@ def infer_segmentation_frame(
         result = segmenter.predict(frame, text_prompts=text_queries)
     labels = text_queries or []
     if len(labels) == 1:
-        labels = [labels[0] for _ in range(len(result.masks or []))]
+        masks = result.masks if result.masks is not None else []
+        labels = [labels[0] for _ in range(len(masks))]
     return draw_masks(frame, result.masks, labels=labels), result