typo in recent cpp API improvements
typo in recent cpp API improvements

We had G_VALUE_TYPE instead of G_OBJECT_TYPE, oops. Thanks @lovell.

see https://github.com/libvips/libvips/pull/1812

lovell/libvips,lovell/libvips,jcupitt/libvips,jcupitt/libvips,lovell/libvips,jcupitt/libvips,jcupitt/libvips,lovell/libvips