Update PngDecoderCore.cs

src/ImageSharp/Formats/Png/PngDecoderCore.cs

@@ -746,7 +746,14 @@ namespace SixLabors.ImageSharp.Formats.Png
             ReadOnlySpan<byte> trimmed = defilteredScanline.Slice(1, defilteredScanline.Length - 1);
 
             // Convert 1, 2, and 4 bit pixel data into the 8 bit equivalent.
-            ReadOnlySpan<byte> scanlineSpan = this.TryScaleUpTo8BitArray(trimmed, this.bytesPerScanline, this.header.BitDepth, out IMemoryOwner<byte> buffer)
+            IMemoryOwner<byte> buffer = null;
+            try
+            {
+                ReadOnlySpan<byte> scanlineSpan = this.TryScaleUpTo8BitArray(
+                    trimmed,
+                    this.bytesPerScanline,
+                    this.header.BitDepth,
+                    out buffer)
                 ? buffer.GetSpan()
                 : trimmed;
 
@@ -816,9 +823,12 @@ namespace SixLabors.ImageSharp.Formats.Png
 
                         break;
                 }
-
+            }
+            finally
+            {
                 buffer?.Dispose();
             }
+        }
 
         /// <summary>
         /// Decodes and assigns marker colors that identify transparent pixels in non indexed images.