Fix warning about use of uninitialized variable

qwaylandwindow.cpp:443:25: warning: ‘transform’ may be used uninitialized in this function [-Wmaybe-uninitialized]

Change-Id: Ic0a96cfda35d331c9957a527eea7f8b987191b5f
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>

src/plugins/platforms/wayland/qwaylandwindow.cpp

@@ -438,6 +438,8 @@ void QWaylandWindow::handleContentOrientationChange(Qt::ScreenOrientation orient
         case Qt::InvertedPortraitOrientation:
             transform = isPortrait ? WL_OUTPUT_TRANSFORM_180 : WL_OUTPUT_TRANSFORM_270;
             break;
+        default:
+            Q_UNREACHABLE();
     }
     set_buffer_transform(transform);
     // set_buffer_transform is double buffered, we need to commit.