powerprofileconfig: Use m_profileCombo as the watcher's parent
m_profileCombo could be an invalid pointer, because when clicking an
item, QAbstractItemView::clicked and QAbstractItemView::activated in
systemsettings both will be emitted, and IconMode::changeModule will be
called twice, and closeModules() will free m_profileCombo in the
second call, which will crash systemsettings.
To fix the crash, set the watcher's parent to m_profileCombo, so when
m_profileCombo is destroyed, the watcher is also destroyed and the
connection is disconnected to prevent modification to the old m_profileCombo.