Any reason to handle null this in ExpressionExtensions.Transform ?

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Why no throw exception?

[Pure]
		public static Expression Transform([CanBeNull] this Expression expr, [NotNull] Func<Expression, Expression> func)
		{
			if (func == null) throw new ArgumentNullException(nameof(func));

			return TransformInternal(expr, func);
		}

		[CanBeNull]
		private static Expression TransformInternal([CanBeNull] this Expression expr, [NotNull] Func<Expression, Expression> func)
		{
			if (expr == null)
				return null;
...
}

[ig-sinicyn]

@igor-tkachev Can you check this?

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@igor-tkachev Ping