Baloo engine: treat every non-success code as a failure
Treating only MDB_NOTFOUND as an error leads to use of uninitliazed
pointers and handle IDs in other cases (e.g. when get fails with
MDB_BAD_TXN) and wreaks havoc in the application.
Reviewers: Baloo, bruns, poboiko
Reviewed By: Baloo, bruns
Subscribers: cullmann, ngraham, bruns, kde-frameworks-devel, Baloo
Differential Revision: https://phabricator.kde.org/D18664