Fix failure on loading empty file
Fix failure on loading empty file

Re: brofield/simpleini#19

The Windows, Unicode, UTF-8 version of SizeFromStore returns failure when
given zero-length data. Fix by moving a_uDataLen == 0 check to after the
UTF-8 BOM removal.

aseprite/simpleini,brofield/simpleini,brofield/simpleini,aseprite/simpleini