[Process] Check if the pipe array is empty before calling stream_select()

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #9280
| License       | MIT
| Doc PR        | 


ProcessPipes generates a warning frequently which can cause issues for custom shutdown functions. Adding a check to see if the pipe array is empty should be functionally equivalent without having to generate the error.

Fixes: #9280