mainmenu: Clear search edit on hide, rather than on show.
mainmenu: Clear search edit on hide, rather than on show.

This prevents the fade-out animation of the "clear" icon which
would occur when the menu was shown the next time after performing
a search.  IMHO, animations on newly-shown widgets are undesirable.

stefonarch/lxqt-panel,stefonarch/lxqt-panel,stefonarch/lxqt-panel