Fix GetWritableRegion write-back (#2456)

Ryujinx.Memory/IVirtualMemoryManager.cs

@@ -66,7 +66,9 @@ namespace Ryujinx.Memory
             {
                 int copySize = (int)Math.Min(MaxChunkSize, size - subOffset);
 
-                GetWritableRegion(va + subOffset, copySize).Memory.Span.Fill(0);
+                using var writableRegion = GetWritableRegion(va + subOffset, copySize);
+
+                writableRegion.Memory.Span.Fill(0);
             }
         }
 

Ryujinx.Memory/MemoryBlock.cs

@@ -333,7 +333,7 @@ namespace Ryujinx.Memory
         /// <exception cref="InvalidMemoryRegionException">Throw when either <paramref name="offset"/> or <paramref name="size"/> are out of range</exception>
         public WritableRegion GetWritableRegion(ulong offset, int size)
         {
-            return new WritableRegion(this, offset, GetMemory(offset, size));
+            return new WritableRegion(null, offset, GetMemory(offset, size));
         }
 
         /// <summary>