Rejections are not supported to be saved, but it does happen occasionally because of dirty diffs (see e.g. T340461: 'Add image' claims '1 image' was added, only dummy change saved). We should probably do something about that, but as a trivial improvement, we should just make sure the edit summary is set appropriately for rejections (instead of the current Added 1 image.).

This pertains to both article-level and section-level image tasks.