We ran into this when testing uBlock. The logger / zap / picker buttons in the action popup try to find and select an existing tab before opening a new one.

Bug in Fenix: https://github.com/mozilla-mobile/fenix/issues/8467

The error:

BrowserApp.selectTab is not a function ext-tabs.js:408
    update chrome://geckoview/content/ext-tabs.js:408
    update self-hosted:878
    result resource://gre/modules/ExtensionParent.jsm:1106
    withPendingBrowser resource://gre/modules/ExtensionParent.jsm:737
    result resource://gre/modules/ExtensionParent.jsm:1106
    callAndLog resource://gre/modules/ExtensionParent.jsm:1068
    recvAPICall resource://gre/modules/ExtensionParent.jsm:1105
    AsyncFunctionNext self-hosted:696

We also see:

Error: Invalid tab ID: 10069

I mentioned this before at https://bugzilla.mozilla.org/show_bug.cgi?id=1565536#c1

Before this patch, the TabDelegate was "special" as in it had just one global
delegate that receives events for all extensions and sessions. This was done to
allow mochitests to call tabs.create and tabs.remove.

This hack is no longer needed as now we can notify the embedding layer that a
new extension has been installed and we have a way to list currently installed
extensions.

This patch makes TabDelegate behave the same as the other delegates
(ActionDelegate and MessageDelegate) and will allow further simplications of
the WebExtension Delegate code.

Backed out 3 changesets (Bug 1616625) for causing xpcshell failures in xpcshell.ini:toolkit/components/extensions/test/xpcshell/test_csp_custom_policies.js CLOSED TREE

https://treeherder.mozilla.org/#/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception&classifiedState=unclassified&selectedJob=291526981

https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=291526981&repo=autoland&lineNumber=2838

Thanks.

https://hg.mozilla.org/mozilla-central/rev/7772ff1517fd
https://hg.mozilla.org/mozilla-central/rev/9289e0f9f2c6
https://hg.mozilla.org/mozilla-central/rev/0636bd0463dd