Remove empty exception constructors

Ensure that we provide a message when throwing.

src/ImageSharp/Common/Exceptions/ImageFormatException.cs

@@ -11,13 +11,6 @@ namespace SixLabors.ImageSharp
     /// </summary>
     public sealed class ImageFormatException : Exception
     {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ImageFormatException"/> class.
-        /// </summary>
-        public ImageFormatException()
-        {
-        }
-
         /// <summary>
         /// Initializes a new instance of the <see cref="ImageFormatException"/> class with the name of the
         /// parameter that causes this exception.

src/ImageSharp/Common/Exceptions/ImageProcessingException.cs

@@ -10,13 +10,6 @@ namespace SixLabors.ImageSharp
     /// </summary>
     public sealed class ImageProcessingException : Exception
     {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ImageProcessingException"/> class.
-        /// </summary>
-        public ImageProcessingException()
-        {
-        }
-
         /// <summary>
         /// Initializes a new instance of the <see cref="ImageProcessingException"/> class with the name of the
         /// parameter that causes this exception.
@@ -39,4 +32,4 @@ namespace SixLabors.ImageSharp
         {
         }
     }
-}
+}