Fix invalid indices when content is not long enough

Signed-off-by: Marcel Müller <neikos@neikos.email>

tests/checks.rs

@@ -0,0 +1,14 @@
+#[test]
+fn check_files() {
+    let files = std::fs::read_dir("tests/checks/").unwrap();
+
+    for file in files {
+        let input = std::fs::read_to_string(file.unwrap().path()).unwrap();
+
+        let parsed = nomo::parser::parse(input.into()).unwrap();
+
+        let ast = nomo::ast::parse(parsed.tokens()).unwrap();
+
+        let _emit = nomo::emit::emit_machine(ast);
+    }
+}