str_to_term in serde code doesn't fall back to string

[benhaney]

Quick drive-by issue just to note that this function doesn't behave like its comment says it does:

rustler/rustler/src/serde/atoms.rs

Lines 22 to 37 in ef20458

	/**
	* Attempts to create an atom term from the provided string (if the atom already exists in the atom table). If not, returns a string term.
	*/
	pub fn str_to_term<'a>(env: &Env<'a>, string: &str) -> Result<Term<'a>, Error> {
	if string == "Ok" {
	Ok(ok().encode(*env))
	} else if string == "Err" {
	Ok(error().encode(*env))
	} else {
	match Atom::try_from_bytes(*env, string.as_bytes()) {
	Ok(Some(term)) => Ok(term.encode(*env)),
	Ok(None) => Err(Error::InvalidStringable),
	_ => Err(Error::InvalidStringable),
	}
	}
	}

Specifically, it says it returns a string term if there isn't already an existing atom:

rustler/rustler/src/serde/atoms.rs

Line 23 in ef20458

* Attempts to create an atom term from the provided string (if the atom already exists in the atom table). If not, returns a string term.

but then doesn't do that and just returns an error instead:

rustler/rustler/src/serde/atoms.rs

Line 33 in ef20458

Ok(None) => Err(Error::InvalidStringable),