Use an appropriate method to show modal dialog

PR #16809.

src/gui/mainwindow.cpp

@@ -971,7 +971,6 @@ void MainWindow::askRecursiveTorrentDownloadConfirmation(BitTorrent::Torrent *co
         , tr("The torrent '%1' contains torrent files, do you want to proceed with their download?").arg(torrent->name())
         , QMessageBox::NoButton, this);
     confirmBox->setAttribute(Qt::WA_DeleteOnClose);
-    confirmBox->setModal(true);
 
     const QPushButton *yes = confirmBox->addButton(tr("Yes"), QMessageBox::YesRole);
     /*QPushButton *no = */ confirmBox->addButton(tr("No"), QMessageBox::NoRole);
@@ -983,7 +982,7 @@ void MainWindow::askRecursiveTorrentDownloadConfirmation(BitTorrent::Torrent *co
         if (button == never)
             Preferences::instance()->disableRecursiveDownload();
     });
-    confirmBox->show();
+    confirmBox->open();
 }
 
 void MainWindow::handleDownloadFromUrlFailure(const QString &url, const QString &reason) const

src/gui/transferlistwidget.cpp

@@ -333,7 +333,6 @@ void TransferListWidget::setSelectedTorrentsLocation()
     auto fileDialog = new QFileDialog(this, tr("Choose save path"), oldLocation.data());
     fileDialog->setAttribute(Qt::WA_DeleteOnClose);
     fileDialog->setFileMode(QFileDialog::Directory);
-    fileDialog->setModal(true);
     fileDialog->setOptions(QFileDialog::DontConfirmOverwrite | QFileDialog::ShowDirsOnly | QFileDialog::HideNameFilterDetails);
     connect(fileDialog, &QDialog::accepted, this, [this, fileDialog]()
     {
@@ -353,7 +352,7 @@ void TransferListWidget::setSelectedTorrentsLocation()
         }
     });
 
-    fileDialog->show();
+    fileDialog->open();
 }
 
 void TransferListWidget::pauseAllTorrents()