`gx_binres_theme_load()` sizes its theme buffer for the theme it was asked for, and allocates it even when the resource holds no theme with…

`gx_binres_theme_load()` sizes its theme buffer for the theme it was asked for, and allocates it even when the resource holds no theme with that id. A theme id at or past the theme count declared by the resource gets a buffer of zero bytes. The load pass then walks past the end of the theme table, takes whatever follows as a theme header, and writes a `GX_THEME` and its tables into that zero-byte buffer.