Allow implicit conversion of null arrays to empty Memory instances

Author: GrabYourPitchforks

src/mscorlib/shared/System/Memory.cs

@@ -106,7 +106,7 @@ private Memory(object obj, int index, int length)
         /// <summary>
         /// Defines an implicit conversion of an array to a <see cref="Memory{T}"/>
         /// </summary>
-        public static implicit operator Memory<T>(T[] array) => new Memory<T>(array);
+        public static implicit operator Memory<T>(T[] array) => (array != null) ? new Memory<T>(array) : default;
 
         /// <summary>
         /// Defines an implicit conversion of a <see cref="ArraySegment{T}"/> to a <see cref="Memory{T}"/>

src/mscorlib/shared/System/ReadOnlyMemory.cs

@@ -97,7 +97,7 @@ internal ReadOnlyMemory(object obj, int start, int length)
         /// <summary>
         /// Defines an implicit conversion of an array to a <see cref="ReadOnlyMemory{T}"/>
         /// </summary>
-        public static implicit operator ReadOnlyMemory<T>(T[] array) => new ReadOnlyMemory<T>(array);
+        public static implicit operator ReadOnlyMemory<T>(T[] array) => (array != null) ? new ReadOnlyMemory<T>(array) : default;
 
         /// <summary>
         /// Defines an implicit conversion of a <see cref="ArraySegment{T}"/> to a <see cref="ReadOnlyMemory{T}"/>