MainWindow: Change comma position in initialization list

Summary:
Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

MainWindow: Move m_theme to initialization list

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

FileLoader: Move lastPerc inside file open function

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Reviewers: tcanabrava, rizzitello, laysrodrigues

Reviewed By: rizzitello, laysrodrigues

Differential Revision: https://phabricator.kde.org/D12667