fix crash of video in case of no detected label.

Author: ChipsSpectre

efficientdet_test_videos.py

@@ -57,7 +57,7 @@
 def display(preds, imgs):
     for i in range(len(imgs)):
         if len(preds[i]['rois']) == 0:
-            continue
+            return imgs[i]
 
         for j in range(len(preds[i]['rois'])):
             (x1, y1, x2, y2) = preds[i]['rois'][j].astype(np.int)