Don't perform wayland specific fixes when on X

Summary:
fd2e850156ac7aa9c9dc2cf46652b2a1f1fc3a07 introduces some behaviour
changes that affect X even though they should be only Wayland related.

BUG: 381130

Reviewers: #plasma

Subscribers: graesslin, plasma-devel, #frameworks

Tags: #plasma, #frameworks

Differential Revision: https://phabricator.kde.org/D6776

src/plasmaquick/dialog.cpp

@@ -1157,7 +1157,7 @@ bool Dialog::event(QEvent *event)
     if (event->type() == QEvent::Expose) {
         auto ee = static_cast<QExposeEvent*>(event);
 
-        if (ee->region().isNull()) {
+        if (!KWindowSystem::isPlatformWayland() || ee->region().isNull()) {
             return QQuickWindow::event(event);
         }