QmlDesigner: Close PopupDialog on QtDS inactive

Close a PopupDialog whenever the main application becomes inactive by
e.g. focusing another app. This prevents the PopupDialog being drawn
on top of that any other application.

Task-number: QDS-11870
Change-Id: I2d5dce4a7a54d43382010dedee3ba214a70d2eb8
Reviewed-by: Qt CI Patch Build Bot <ci_patchbuild_bot@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

share/qtcreator/qmldesigner/propertyEditorQmlSources/imports/StudioControls/PopupDialog.qml

@@ -286,8 +286,10 @@ QtObject {
             enabled: root.visible
 
             function onFocusWindowChanged(focusWindow) {
-                if (!focusWindow)
+                if (!focusWindow) {
+                    root.close()
                     return
+                }
 
                 if (root.keepOpen)
                     return