Fixes: #13278
The fallback default keyboard corresponding to an uninitialized cookie is `Keyboard_us:en`. This should only occur if the site actually registers its stub before initialization - and we weren't checking/filtering for this properly.
The error itself only occurred if there _were_ stubs pre-registered before init - if none existed, the error does not result.
Keyman makes it possible for you to type in any language on Windows, macOS, Linux, iPhone, iPad, Android tablets and phones, and even instantly in your web browser. Create keyboard layouts with Keyman Developer and share them with the community in the keyboards repository. The Keyman Community have already contributed keyboard layouts for over 2,000 languages!
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Keyman is an open source project distributed under the MIT license.