4.3: Fix subget returning entries that are not actually subentries

A user can specify that an element must have a certain attribute to be considered a subentry.
subget did not respect this, so when using it to find potential subentries, there could be entries in the list that should not be there (because they were missing the attribute).

- also fix some linter warnings and a forgotten argument that could lead to an exception when getting an entry's history