To make it possible to support a larger structure.

Fixes a scan-build warning.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=51640

Similar to 35f9091b, IsRectEmpty() is the wrong way to check if padding is empty.

base_url was never freed, and can simply be enlarged instead of copying
it to a new buffer.

Instead of ERROR_SUCCESS.

If fileW is not null, it is freed at the end of the function.

If read_identity returns FALSE, it has already called clear_identity.