#14238 Now the file completion is triggered on a custom command after the first parameter. (#14481)

- this PR should close #14238

# Description
Solved as described here (First suggestion):
https://github.com/nushell/nushell/issues/14238#issuecomment-2506387012

Below I make the example from the issue, it shows that the completion
now works past the first parameter.
```
~/Projects/nushell> def list [...args] {                                                                                                  11/30/2024 03:21:24 PM
:::     $args
:::     | each {
:::         open $args
:::     }
::: }
~/Projects/nushell> cd tests/fixtures/completions/                                                                                        11/30/2024 03:25:24 PM
~/Projects/nushell/tests/fixtures/completions| list custom_completion.nu                                                                  11/30/2024 03:25:35 PM
another/               custom_completion.nu   directory_completion/  nushell
test_a/                test_b/                .hidden_file           .hidden_folder/
``` 

# User-Facing Changes
The changes introduced to completions in
`baadaee0163a5066ae73509ff6052962b3422673` now does not return if it did
not find "Operator completions".

This could have impact on more than just custom commands, but it could
be seemed as making everything a bit more robust.

# Tests + Formatting
I ran all of:  
- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used` to
check that you're using the standard code style
- `cargo test --workspace` to check that all tests pass (on Windows make
sure to [enable developer
mode](https://learn.microsoft.com/en-us/windows/apps/get-started/developer-mode-features-and-debugging))
- `cargo run -- -c "use toolkit.nu; toolkit test stdlib"` to run the
tests for the standard library

# After Submitting
I do not think there is any need to update [the
documentation](https://github.com/nushell/nushell.github.io), right?

---------

Co-authored-by: Daniel Winther Petersen <daniel.winther.petersen@subaio.com>

crates/nu-cli/src/completions/completer.rs

@@ -297,7 +297,7 @@ impl NuCompleter {
                                     let mut completer =
                                         OperatorCompletion::new(pipeline_element.expr.clone());
 
-                                    return self.process_completion(
+                                    let operator_suggestion = self.process_completion(
                                         &mut completer,
                                         &working_set,
                                         prefix,
@@ -305,6 +305,9 @@ impl NuCompleter {
                                         fake_offset,
                                         pos,
                                     );
+                                    if !operator_suggestion.is_empty() {
+                                        return operator_suggestion;
+                                    }
                                 }
                             }
                         }