fix bugs

app.py

@@ -221,7 +221,7 @@ def build_demo(embed_mode):
                     label="Preprocess for non-square image", visible=False)
 
                 gr.Examples(examples=[
-                    ["./examples/image-text/demo_example.png", "When the canister is momentarily stopped by the spring, by what distance $d$ is the spring compressed?"],
+                    ["./examples/image-text/demo_example.jpg", "When the canister is momentarily stopped by the spring, by what distance $d$ is the spring compressed?"],
                 ], inputs=[imagebox, textbox], label='Examples')
 
             with gr.Column(scale=8):