screencopy: don't make a buffer param mismatch a protocol error

[emersion]

Right now if a client tries to copy a buffer with invalid params, a protocol error is sent.

This makes it mandatory for the client to wait for the buffer event containing the buffer params prior to sending the copy request. If invalid buffer params caused a failed event, a client could only wait for buffer params on the first frame and then re-use the previous params (retrying on failure if the buffer params changed). This would avoid one roundtrip per frame.

This would not be a breaking change.

[emersion]

wlr-protocols has migrated to gitlab.freedesktop.org. This issue has been moved to:

https://gitlab.freedesktop.org/wlroots/wlr-protocols/-/issues/82