isNullValue fails on newly-created entity for null attributes

[MordantWastrel]

In working with a Quick entity and mementifier, we've noticed that if you call getMemento() on an entity you just created where some of the values are not populated (i.e. actually null rather than the empty-string null you get when loading an entity from the DB), this function on BaseEntity will fail:

	public boolean function isNullValue( required string key, any value ) {
		param arguments.value = invoke( this, "get" & arguments.key );
		var alias             = retrieveAliasForColumn( arguments.key );
		if ( !isSimpleValue( arguments.value ) ) {
			return false;
		}
		return variables._nullValues.keyExists( alias ) &&
		compare( variables._nullValues[ alias ], arguments.value ) == 0;
	}

With the error: The required parameter [arguments.value] was not provided

In other words, if your User entity has firstname and lastname and you create a new user with only a firstname and then call getMemento() it will fail on that IsNullValue function call for lastname.

Not a problem when loading an existing entity because hydration takes care of all the null values.