Firefox Multi-Account Containers results in 2 errors in Firefox, including "can't access property 'isAdoptingTab', this.window.gBrowserInit is undefined"

[Gitoffthelawn]

Before submitting a bug report

• I updated to the latest version of Multi-Account Container and tested if I can reproduce the issue
• I searched for existing reports to see if it hasn't already been reported

Step to reproduce

With no other extensions enabled, Firefox Multi-Account Containers 8.3.6 in Firefox 148.0 results in these two (2) errors on Firefox launch, visible in Firefox's multiprocess browser console:

1. can't access property "isAdoptingTab", this.window.gBrowserInit is undefined  -  ext-browser.js:1203:9
    get activeTab chrome://browser/content/parent/ext-browser.js:1203
    candidates chrome://extensions/content/parent/ext-tabs-base.js:2118
    InterpretGeneratorResume self-hosted:1312
    next self-hosted:1233
    query chrome://extensions/content/parent/ext-tabs-base.js:2140
    InterpretGeneratorResume self-hosted:1312
    next self-hosted:1233
    from self-hosted:513
    query chrome://browser/content/parent/ext-tabs.js:1062
    result resource://gre/modules/ExtensionParent.sys.mjs:1223
    withCallContextData resource://gre/modules/ExtensionParent.sys.mjs:666
    result resource://gre/modules/ExtensionParent.sys.mjs:1222
    withPendingBrowser resource://gre/modules/ExtensionParent.sys.mjs:676
    result resource://gre/modules/ExtensionParent.sys.mjs:1221
    callAndLog resource://gre/modules/ExtensionParent.sys.mjs:1172
    recvAPICall resource://gre/modules/ExtensionParent.sys.mjs:1220
    AsyncFunctionNext self-hosted:780

2. Uncaught (in promise) Error: An unexpected error occurred  -  undefined

Can these be mitigated?

STR:

1. Launch Firefox 148.0
2. Install Firefox Multi-Account Containers 8.3.6 in Firefox
3. Close Firefox
4. Launch Firefox
5. Open Firefox's multiprocess browser console
6. Observe the errors described above

Actual behavior

Errors described above.

Expected behavior

No errors.