Clean up after resize.

Former-commit-id: ecde7b51da9a00e7b83a6cd3be0f17bc4809ce66
Former-commit-id: 7972863246f8a461e065f0fd53938c734f42df4d
Former-commit-id: b266214b444bc204f552ebba19f03a9aca791ac3

src/ImageProcessorCore/Samplers/Resize.cs

@@ -184,6 +184,9 @@ namespace ImageProcessorCore.Samplers
             {
                 target.ClonePixels(target.Width, target.Height, source.Pixels);
             }
+
+            // Clean up
+            this.firstPass?.Dispose();
         }
     }
 }