Update app.py

app.py

@@ -64,7 +64,7 @@ def determine_pause(audio:np.ndarray,sampling_rate:int,state:AppState) -> bool:
 
 def process_audio(audio:tuple,state:AppState,image:Image):
     if state.recording:  # Kiểm tra state.stream:
-        if state.stream:
+        if state.stream is not None:
             state.stream = np.concatenate((state.stream, audio[1]))
         else:
             state.stream = audio[1]