Resolve PR issues

src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs

@@ -67,7 +67,7 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
 
     private sealed class LifetimeGuard : RefCountedMemoryLifetimeGuard
     {
-        private byte[] array;
+        private byte[]? array;
 
         public LifetimeGuard(byte[] array) => this.array = array;
 
@@ -78,7 +78,8 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
             // This is not ideal, but subsequent leaks will end up returning arrays to per-cpu buckets,
             // meaning likely a different bucket than it was rented from,
             // but this is PROBABLY better than not returning the arrays at all.
-            ArrayPool<byte>.Shared.Return(this.array);
+            ArrayPool<byte>.Shared.Return(this.array!);
+            this.array = null;
         }
     }
 }

src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs

@@ -48,6 +48,6 @@ internal abstract partial class MemoryGroup<T>
             return ((IList<Memory<T>>)this.source).GetEnumerator();
         }
 
-        public override void Dispose() => this.View?.Invalidate();
+        public override void Dispose() => this.View.Invalidate();
     }
 }