Summary:
By not checking the return of runJob(), the slave might call finished() after already having called error() in handleError().
See T7995 for futher information.

Reviewers: elvisangelaccio, dvratil

Reviewed By: elvisangelaccio

Subscribers: dvratil, #kio_gdrive

Tags: #kio_gdrive

Differential Revision: https://phabricator.kde.org/D22462