Intialize m_lastPosition
Summary:
Avoid uninitialized usage of m_lastPosition.
Test Plan: Run kwrite under valgrind, no message.
Reviewers: KTextEditor, cullmann, volkov
Reviewed By: KTextEditor, cullmann, volkov
Subscribers: kwrite-devel, kde-frameworks-devel
Tags: Kate, Frameworks
Differential Revision: https://phabricator.kde.org/D15420