Added empty stream as fallback path

Author: Sergio0694

Microsoft.Toolkit.HighPerformance/Streams/MemoryStream.cs

@@ -34,7 +34,8 @@ public static Stream Create(ReadOnlyMemory<byte> memory, bool isReadOnly)
                 return new MemoryStream<MemoryManagerOwner>(memoryManagerSpanSource, isReadOnly);
             }
 
-            throw new NotImplementedException();
+            // Return an empty stream if the memory was empty
+            return new MemoryStream<ArrayOwner>(ArrayOwner.Empty, isReadOnly);
         }
 
         /// <summary>
@@ -61,7 +62,8 @@ public static Stream Create(IMemoryOwner<byte> memoryOwner)
                 return new IMemoryOwnerStream<MemoryManagerOwner>(memoryManagerSpanSource, false, memoryOwner);
             }
 
-            throw new NotImplementedException();
+            // Return an empty stream if the memory was empty
+            return new IMemoryOwnerStream<ArrayOwner>(ArrayOwner.Empty, false, memoryOwner);
         }
     }
 }

Microsoft.Toolkit.HighPerformance/Streams/Sources/ArrayOwner.cs

@@ -38,6 +38,15 @@ public ArrayOwner(byte[] array, int offset, int length)
             this.length = length;
         }
 
+        /// <summary>
+        /// Gets an empty <see cref="ArrayOwner"/> instance.
+        /// </summary>
+        public static ArrayOwner Empty
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => new ArrayOwner(Array.Empty<byte>(), 0, 0);
+        }
+
         /// <inheritdoc/>
         public int Length
         {