Sketchpad demo doesn't work after clicking another tab

[aliabd]

Describe the bug

The pictionary demo on the landing page at https://gradio.app has a bug where it doesn't work if you click on a different tab and then back to it.

Is there an existing issue for this?

• I have searched the existing issues

Reproduction

See https://gradio.app

Screenshot

Screen.Recording.2022-08-05.at.3.36.46.PM.mov

Logs

Uncaught DOMException: Failed to execute 'drawImage' on 'CanvasRenderingContext2D': The image argument is a canvas element with a width or height of 0.
    at saveLine (https://gradio.s3-us-west-2.amazonaws.com/3.1.1/assets/index.9d04c032.js:970:15)
    at https://gradio.s3-us-west-2.amazonaws.com/3.1.1/assets/index.9d04c032.js:790:4
    at Array.forEach (<anonymous>)
    at draw_lines (https://gradio.s3-us-west-2.amazonaws.com/3.1.1/assets/index.9d04c032.js:776:9)
    at load_save_data (https://gradio.s3-us-west-2.amazonaws.com/3.1.1/assets/index.9d04c032.js:760:4)
    at handle_canvas_resize (https://gradio.s3-us-west-2.amazonaws.com/3.1.1/assets/index.9d04c032.js:844:3)
    at ResizeObserver.<anonymous> (https://gradio.s3-us-west-2.amazonaws.com/3.1.1/assets/index.9d04c032.js:701:5)

System Info

Chrome

Severity

serious, but I can work around it

[abidlabs]

Happy to report that this problem is fixed in 3.4 (cc @pngwn)!