File size doesn't show under attachment details using Stateless mode.

[oalexdoda]

[alimuzzaman]

@Abruptive Problem has been fixed.

Please test and let us know.
You can get the fixed version from here https://github.com/wpCloud/wp-stateless/tree/c91778ff5a42e081bf0f4f614531e11c6fd154fa

The fix will be included in the next release.