gtad.yaml: Fixes around defaultValue
gtad.yaml: Fixes around defaultValue

1. defaultValue now preempts Omittable<>
2. Fixed the problem when defaultValue was provided but initializer was empty
(a case for int's, bool's etc.)

Fxrh/libqmatrixclient,QMatrixClient/libqmatrixclient,QMatrixClient/libqmatrixclient