wasm: fix size of QDialogs

We can simply propagate the minimum window size.

Pick-to: 6.2 5.15
Fixes: QTBUG-83503
Change-Id: Ia9f67c92ca37fd0f4e89f08e5153e12c1385f6f8
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/plugins/platforms/wasm/qwasmwindow.cpp

@@ -171,7 +171,12 @@ WId QWasmWindow::winId() const
 
 void QWasmWindow::propagateSizeHints()
 {
-// get rid of base class warning
+    QRect rect = windowGeometry();
+    if (rect.size().width() < windowMinimumSize().width()
+        && rect.size().height() < windowMinimumSize().height()) {
+        rect.setSize(windowMinimumSize());
+        setGeometry(rect);
+    }
 }
 
 void QWasmWindow::injectMousePressed(const QPoint &local, const QPoint &global,