Fix a panic bug in platform ansi logic (Closes #9448) (#9458)

Fixes #9448 

# Description
Attempts to fix a bug from the linked issue.

# User-Facing Changes
 - The editor doesn't crash on wrong commands
# Tests + Formatting

Tests cover my changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect -A clippy::result_large_err` to check that
you're using the standard code style
- `cargo test --workspace` to check that all tests pass
- `cargo run -- crates/nu-std/tests/run.nu` to run the tests for the
standard library

crates/nu-command/tests/commands/platform/mod.rs

@@ -1,2 +1,3 @@
+mod ansi_;
 mod du;
 mod kill;