Standard says, the function XkbGetNamedGeometry can return BadName, but besides it the function can also return BadImplementation and BadAccess.
BadImplementation is a generic error that can be returned by any function. If you encounter such an error, it's usually best to file the bug against the server with a test case on how to reproduce. BadAccess is similar, being a generic error if the client calls an XKB function without being initialized.
Why I've posted it as a bug, because there are a lot functions in the same XKBlib.pdf document, where the information about BadImplementation and BadAccess errors is presented. For example XkbGetIndicatorMap(), XkbChangeIndicators(), XkbGetControls() and others.
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