If we save in one terp, restore in the second terp, save in the second terp, then restore in the first terp, when different rules apply about displaying banners in the two terps, then windows removed in the second terp could still be marked as inited_ in the restore file that comes back to the first terp. To get round this, on restoration we ensure that each CustomBanner's inited_ property in fact corresponds to whether it has an active handle_, otherwise the attempt to reinitialize missing banners might fail.

customBannerRestoreRemove :   PostRestoreObject