I wanted to report this question on Apple Stack Exchange as off topic, but when I tapped "flag" I get this error message:
I am using iOS 8.1.1 and the latest version of the Stack Exchange App (1.2.1)
This question was caused by the question being closed while you were looking at it. All the close options disappeared so the API could not find a matching option.
For a while the app has been displaying this message:
The app submitted an invalid request. Please let us know on meta.
Now it will display either of the following depending on whether you started from Close or Flag:
This close option is no longer available. The question may have already been closed.
This flag option is no longer available.