TBB 13.0a2: TypeError: channel.loadInfo.browsingContext.topChromeWindow.gBrowser is undefined

Since Tor Browser version 13.0a2, this error message appears in the Browser Console when trying to update the uBlock Origin filter lists. After each failed connection, the following message is printed to the console:

TorDomainIsolator: Error while setting a new proxy TypeError: channel.loadInfo.browsingContext.topChromeWindow.gBrowser is undefined #getBrowserForChannel resource://gre/modules/TorDomainIsolator.sys.mjs:456 #proxyFilter resource://gre/modules/TorDomainIsolator.sys.mjs:316 applyFilter resource://gre/modules/TorDomainIsolator.sys.mjs:278 TorDomainIsolator.sys.mjs:335

uBO filter list update works fine in TBB 13.0a1.