WindowManager: Fix error handling for #openWindow with string argument
WindowManager: Fix error handling for #openWindow with string argument

`lifecycle.opening` is a Promise here, it can't be rejected.
We want to reject the underlying Deferred.

Bug: T166631
Change-Id: I6237c602d334f044e8b745e46f5bb80276d2626b

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui