Slack as a Gnome Web Web-Application keeps asking for permission to show desktop notifications

I'm using Gnome Web (web browser) to run slack as a web application so that I can search for it as an app in the Ubuntu Gnome activities screen. This works well but everytime I start the Web App I get asked by if slack.com can set desktop notifications.

I also use web.skype.com as a web application too and was only ever asked once if skype.com could set desktop notifications.

Does anyone know what the problem might be or how I can fix it.

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