Fix the bug that causes an infinite loop when the total number of frames in the video does not exceed 11.

eg, the video has 11 frames, when select the NO.6 frame, `while abs(random_element - img_idx) <= 5:` will result in an infinite loop

train_codes/DataLoader.py

@@ -135,7 +135,7 @@ class Dataset(object):
             #随机选择某个video里
             vidname = self.all_videos[idx].split('/')[-1]
             video_imgs = self.all_img_names[idx]
-            if len(video_imgs) == 0:
+            if len(video_imgs) <= 11:
                 continue
             img_name = random.choice(video_imgs)
             img_idx = int(basename(img_name).split(".")[0])