dcc.Graph rendering goes into infinite error loop when None is returned for Figure

[reggied]

Describe your context Please provide us your environment, so we can easily reproduce the issue.

  dash                           2.18.0
  dash-core-components           2.0.0
  dash-html-components           2.0.0
  dash-table                     5.0.0

• if frontend related, tell us your Browser, Version and OS

  • OS: MacOS/Linux/Windows
  • Browser Chrome
  • Version 128

Describe the bug

When running the below script (which has a bug: graph_selections returns None instead of a Figure) with python3, and displaying in the Chrome browser, the browser tab seems to lock up. If the developer tools are open, one can see the error count rapidly rising with the errors in the screenshot below being repeated over and over again in a tight loop.

from dash import Dash, html, dcc, callback, Output, Input

app = Dash()
app.layout = html.Div([
    html.Button('RUN', id='run-btn', n_clicks=0),
    dcc.Graph(id='graph-container')
])

@callback(
    Output('graph-container', 'figure'),
    Input('run-btn', 'n_clicks'),
)
def graph_selections(n_clicks):
    print(n_clicks)

if __name__ == "__main__":
    app.run(port=8050, host='0.0.0.0', debug=True)

Expected behavior

An error message in the browser, describing the bad return from the callback..

Screenshots