[Cuttlefish] Set context properties before loading file

Summary:
Otherwise we load the file and the context properties are still undefined
leading to a buch ReferenceErrors because they are undefined.

Test Plan: Still works - less warnings

Reviewers: #plasma, ngraham

Reviewed By: ngraham

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D25841