Fix new bookmark query. Fix #16465

QSqlQuery was returning an error : wrong parameters count.
It seems that bindValue was having no effect (no bounded values).
Using prepare after construction seems to solve the problem.

src/app/qgsbookmarks.cpp

@@ -139,9 +139,9 @@ void QgsBookmarks::addClicked()
   QgsMapCanvas *canvas = QgisApp::instance()->mapCanvas();
   Q_ASSERT( canvas );
 
-  QSqlQuery query( "INSERT INTO tbl_bookmarks(bookmark_id,name,project_name,xmin,ymin,xmax,ymax,projection_srid)"
-                   "  VALUES (NULL,:name,:project_name,:xmin,:xmax,:ymin,:ymax,:projection_srid)",
-                   mQgisModel->database() );
+  QSqlQuery query( mQgisModel->database() );
+  query.prepare( "INSERT INTO tbl_bookmarks(bookmark_id,name,project_name,xmin,ymin,xmax,ymax,projection_srid)"
+                 "  VALUES (NULL,:name,:project_name,:xmin,:xmax,:ymin,:ymax,:projection_srid)" );
 
   QString projStr( QLatin1String( "" ) );
   if ( QgsProject::instance() )