make sure to zero window flag for login window

src/widget/loginscreen.cpp

@@ -37,7 +37,7 @@ LoginScreen::LoginScreen(QWidget *parent) :
     ui->setupUi(this);
 
     // permanently disables maximize button https://github.com/tux3/qTox/issues/1973
-    this->setWindowFlags(windowFlags() ^ Qt::WindowMaximizeButtonHint);
+    this->setWindowFlags(windowFlags() &! Qt::WindowMaximizeButtonHint);
     this->setFixedSize(this->size());
 
     connect(&quitShortcut, &QShortcut::activated, this, &LoginScreen::close);
@@ -109,7 +109,7 @@ void LoginScreen::onLoginPageClicked()
 }
 
 void LoginScreen::onCreateNewProfile()
-{   
+{
     QString name = ui->newUsername->text();
     QString pass = ui->newPass->text();