load chroma before the app to avoid the error

app.py

@@ -224,4 +224,5 @@ with gr.Blocks() as demo:
             query_button.click(query_documents, inputs=query_input, outputs=query_output)  
   
 if __name__ == "__main__":  
+    os.system("chroma run --host localhost --port 8000")
     demo.launch()