fix: avoid creating output file on missing RRQ

crates/pfs-tftp-sync/tests/end_to_end.rs

@@ -98,6 +98,25 @@ fn netascii_roundtrip_preserves_newlines_and_cr() {
     stop_server(&shutdown, handle);
 }
 
+#[test]
+fn missing_remote_file_does_not_create_local_file() {
+    let server_root = TempDir::new("pfs_tftp_server_root_missing");
+    let local_root = TempDir::new("pfs_tftp_local_root_missing");
+
+    let (addr, shutdown, handle) = start_server(server_root.path(), true);
+    let client = Client::new(addr, test_client_config());
+
+    let out = local_root.path().join("should_not_exist.bin");
+    assert!(!out.exists());
+
+    let _err = client
+        .get("does_not_exist.bin", &out, Mode::Octet)
+        .unwrap_err();
+    assert!(!out.exists());
+
+    stop_server(&shutdown, handle);
+}
+
 fn test_client_config() -> ClientConfig {
     ClientConfig {
         timeout: Duration::from_millis(200),