The readiness check in Squish for Qt for QML objects determines that the object is not ready for interaction, because it is not visible/accessible on the screen, because its parent clipped it away. What this means, and what to do, probably depends a lot on the situation, which I cannot derive from the information that you have provided.
The script code that you provided should not result in this error, because it does not contain a waitForObject() call.
If you only want to look up an object for something else than interaction, you can consider using the findObject() function, which does a one-time search for the object, and it does not perform the "readiness" check. It will throw an error if no matching object can be found, or return the reference to the found object.