[c#]回傳型態為物件,回傳值為null

        public RectangleF GetCollisionMBR()
        {
            //...
            return bCollisionMBRExists ? rfCollisionBoundingBox : null;
        }            ↑                           ↑
                    bool                        RectangleF

跑出錯誤

Type of conditional expression cannot be determined because there is no
implicit conversion between 'System.Drawing.RectangleF' and '<null>'

請問這裡要怎麼改?
感謝大德!

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