Update NEWS

Author: juliasilge

NEWS.md

@@ -19,7 +19,7 @@
 
 * Re-licensed package from GPL-2 to MIT. See [consent from copyright holders here](https://github.com/tidymodels/parsnip/issues/462).
 
-* `set_mode()` now checks if `mode` is compatible with the model class, similar to `new_model_spec()` (@jtlandis, #467).
+* `set_mode()` now checks if `mode` is compatible with the model class, similar to `new_model_spec()` (@jtlandis, #467). Both `set_mode()` and `set_engine()` now error for `NULL` or missing arguments (#503).
 
 * Re-organized model documentation for `update` methods (#479).