a small bug fix

fixed a bug where the app crashed if the input video file had no audio

app.py

@@ -46,9 +46,9 @@ def process(text_query, full_video_path):
     start_pt, max_end_pt = 0, 10
     input_clip_path = '/tmp/input.mp4'
     # extract the relevant subclip:
-    with VideoFileClip(full_video_path) as video:
-        subclip = video.subclip(start_pt, min(video.duration, max_end_pt))
-        subclip.write_videofile(input_clip_path)
+    full_video = VideoFileClip(full_video_path)
+    subclip = full_video.subclip(start_pt, min(full_video.duration, max_end_pt))
+    subclip.write_videofile(input_clip_path)
         
     checkpoint_path ='./refer-youtube-vos_window-12.pth.tar'
     model, postprocessor = torch.hub.load('mttr2021/MTTR:main','mttr_refer_youtube_vos', get_weights=False)
@@ -125,7 +125,8 @@ def process(text_query, full_video_path):
     # generate and save the output clip:
     output_clip_path = '/tmp/output_clip.mp4'
     clip = ImageSequenceClip(sequence=masked_video, fps=meta['video_fps'])
-    clip = clip.set_audio(AudioFileClip(input_clip_path))
+    if subclip.audio:  # attach audio if original subclip had audio
+      clip = clip.set_audio(subclip.audio)
     clip.write_videofile(output_clip_path, fps=meta['video_fps'], audio=True)
     del masked_video