qt, refactor: Keep OptionsDialog in the main event loop

src/qt/bitcoingui.cpp

@@ -990,10 +990,10 @@ void BitcoinGUI::openOptionsDialogWithTab(OptionsDialog::Tab tab)
     if (!clientModel || !clientModel->getOptionsModel())
         return;
 
-    OptionsDialog dlg(this, enableWallet);
-    dlg.setCurrentTab(tab);
-    dlg.setModel(clientModel->getOptionsModel());
-    dlg.exec();
+    auto dlg = new OptionsDialog(this, enableWallet);
+    dlg->setCurrentTab(tab);
+    dlg->setModel(clientModel->getOptionsModel());
+    GUIUtil::ShowModalDialogAndDeleteOnClose(dlg);
 }
 
 void BitcoinGUI::setNumBlocks(int count, const QDateTime& blockDate, double nVerificationProgress, bool header, SynchronizationState sync_state)