safety check added to get_first_frame

app.py

@@ -201,6 +201,8 @@ def inpaint_video(original_frame_list, mask_list, in_fps, dt_string):
 
 
 def get_first_frame(video):
+    if(video == None):
+        return gr.ImageMask()
     video_capture = cv2.VideoCapture()
     if video_capture.open(video):
         width, height = int(video_capture.get(cv2.CAP_PROP_FRAME_WIDTH)), int(