qt: merge lazy creation of related widgets

the search filter for the advanced preferences tree should always be
lazily created at the same time we lazily create the tree widget itself.
there would never be a situation where this function would find one already
created and not the other. we can thus merge the condition blocks here.

modules/gui/qt/dialogs/preferences/preferences.cpp

@@ -154,7 +154,8 @@ PrefsDialog::~PrefsDialog()
 
 void PrefsDialog::setAdvanced()
 {
-    if ( !tree_filter )
+    /* Lazy creation */
+    if( !advanced_tree )
     {
         tree_filter = new SearchLineEdit( advanced_tree_panel );
         tree_filter->setMinimumHeight( 26 );
@@ -173,15 +174,10 @@ void PrefsDialog::setAdvanced()
 
         QShortcut *search = new QShortcut( QKeySequence( QKeySequence::Find ), tree_filter );
         CONNECT( search, activated(), tree_filter, setFocus() );
-    }
 
-    /* If don't have already and advanced TREE, then create it */
-    if( !advanced_tree )
-    {
-        /* Creation */
         p_list = module_list_get( &count );
         advanced_tree = new PrefsTree( p_intf, advanced_tree_panel, p_list, count );
-        /* and connections */
+
         CONNECT( advanced_tree,
                  currentItemChanged( QTreeWidgetItem *, QTreeWidgetItem * ),
                  this, changeAdvPanel( QTreeWidgetItem * ) );
@@ -189,7 +185,7 @@ void PrefsDialog::setAdvanced()
         advanced_tree_panel->setSizePolicy( QSizePolicy::Maximum, QSizePolicy::Preferred );
     }
 
-    /* If no advanced Panel exist, create one, attach it and show it*/
+    /* Create empty, dummy, controls panel, if needed */
     if( advanced_panels_stack->count() < 1 )
     {
         AdvPrefsPanel *insert = new AdvPrefsPanel( advanced_panels_stack );