mainmenu: Fix visual search problems
mainmenu: Fix visual search problems

1. Remove search QLineEdit parentless show on panel start (menu not built yet)
2. Fix changing cursor to edit

cferr/lxqt-panel,lxde/lxqt-panel,DrTobe/lxqt-panel,stefonarch/lxqt-panel,stefonarch/lxqt-panel,lxde/lxqt-panel,ThomasVie/lxqt-panel-de,pmattern/lxqt-panel,Ilya87/lxqt-panel,DrTobe/lxqt-panel,cferr/lxqt-panel,stefonarch/lxqt-panel,pmattern/lxqt-panel,ThomasVie/lxqt-panel-de,Ilya87/lxqt-panel