Only return the "status" value from "wait" if the result is non-zero. The calling code in the Posix structure converts the status result to a value of type exit_status even if the pid is zero.  The result is ignored in that case but it can result in a Fail exception if the status is invalid.
Only return the "status" value from "wait" if the result is non-zero.
The calling code in the Posix structure converts the status result to a
value of type exit_status even if the pid is zero.  The result is
ignored in that case but it can result in a Fail exception if the
status is invalid.

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