Make saving complete article work in Qt 5.15

The old code works correctly in Qt 4.8.7. But in Qt 5.15.5
selectedFilter is never equal to either element of filters. So HTML Only
is saved no matter which option the user selects.

mainwindow.cc

@@ -3585,7 +3585,8 @@ void MainWindow::on_saveArticle_triggered()
                                            filters.join( ";;" ),
                                            &selectedFilter, options );
 
-  bool complete = ( selectedFilter == filters[ 0 ] );
+  // The " (*.html)" part of filters[i] is absent from selectedFilter in Qt 5.
+  bool const complete = filters.at( 0 ).startsWith( selectedFilter );
 
   if ( !fileName.isEmpty() )
   {