update(app): adjust output message

app.py

@@ -68,10 +68,14 @@ def inference(
 
     progress(1/2, desc='Getting predictions')
     predictions = get_predictions(inputs=inputs, model=model)
-    output_message = ''
-    for i, prediction in enumerate(predictions):
-        output_message += f'{i}. {prediction["label"]} ({prediction["score"]:2f})\n'
-    output_message = output_message.strip()
+
+    if len(predictions) == 0:
+        output_message = 'No sign language detected in the video. Please try again.'
+    else:
+        output_message = 'The top-3 predictions are:\n'
+        for i, prediction in enumerate(predictions):
+            output_message += f'{i+1}. {prediction["label"]} ({prediction["score"]:2f})\n'
+        output_message = output_message.strip()
 
     progress(1/2, desc='Completed')