update gradio cached examples

tts/gradio_api.py

@@ -37,7 +37,7 @@ def model_worker(input_queue, output_queue, device_id):
         task = input_queue.get()
         inp_audio_path, inp_npy_path, inp_text, infer_timestep, p_w, t_w = task
 
-        if inp_npy_path is None or inp_audio_path:
+        if inp_npy_path is None or inp_audio_path is None:
             raise gr.Error("Please provide .wav and .npy file")
         if (inp_audio_path.split('/')[-1][:-4] != inp_npy_path.split('/')[-1][:-4]):
             raise gr.Error(".npy and .wav mismatch")