[AppletQuickItem] Preload applet expander only if not already expanded

When an applet is placed on the desktop and already shows its full representation, like Weather applet,
don't create the expander item.
The DefaultCompactApplet shows the dialog when plasmoid.expanded which will be always the case and you end up with an empty
window randomly showing up on startup.

Differential Revision: https://phabricator.kde.org/D10764