Update app.py

app.py

@@ -32,7 +32,7 @@ with gr.Blocks() as demo:
     with gr.Tab("Charts Generation"):
         with gr.Row():
             dd_label1 = gr.Dropdown(label="Source Column", multiselect=False)
-            dd_label2 = gr.Dropdown(label="Source Column", multiselect=False)
+            dd_label2 = gr.Dropdown(label="Source Column", multiselect=False, value="")
         btn_chart = gr.Button("Generate Bar Plot")
         plt_figure = gr.Plot()