Since the end of last week, every time a user tries to close a powerapps page (either using the direct url https://web.powerapps.com/apps/[GUID] or more importantly, an intranet page which has the app embedded in the PowerApps web part), the browser pops up an annoying message saying:
"Are you sure you want to leave this page? Message from webpage: null"
Is there a fix for this? Other browsers seem OK, but many of our thousands of employees do use IE, so this is a large problem for us.