Legacy screen cannot open another legacy screen as frame from descriptor

[Flaurite]

Steps to reproduce

1. Download attached project: trframe.zip

2. Open "Legacy Demo" screen

AR

java.lang.IllegalStateException: Fragment controllers should inherit ScreenFragment. UI controller is not ScreenFragment - WindowInfo{id='projectsFrame', descriptor=org.dom4j.tree.DefaultElement@11bfbfcb [Element: <screen attributes: [org.dom4j.tree.DefaultAttribute@36d933b5 [Attribute: name template value "com/company/trframe/lgscreen/project/lg-project-screen.xml"], org.dom4j.tree.DefaultAttribute@54d56364 [Attribute: name id value "projectsFrame"]]/>]} LgProjectBrowse
	at io.jmix.ui.sys.FragmentHelper.createController(FragmentHelper.java:63)
	at io.jmix.ui.xml.layout.loader.FragmentComponentLoader.createComponent(FragmentComponentLoader.java:63)
	at io.jmix.ui.xml.layout.loader.LayoutLoader.createComponent(LayoutLoader.java:138)
	at io.jmix.ui.xml.layout.loader.ContainerLoader.createSubComponents(ContainerLoader.java:54)
	at io.jmix.ui.xml.layout.loader.WindowLoader.createContent(WindowLoader.java:54)
	at io.jmix.ui.xml.layout.loader.LayoutLoader.createWindowContent(LayoutLoader.java:160)
	at io.jmix.ui.sys.ScreensImpl.loadWindowFromXml(ScreensImpl.java:321)
	at com.haulmont.cuba.web.sys.CubaScreens.loadWindowFromXml(CubaScreens.java:531)
	at io.jmix.ui.sys.ScreensImpl.createScreen(ScreensImpl.java:201)
	at io.jmix.ui.sys.ScreensImpl.create(ScreensImpl.java:142)

Hint
See FragmentHelper class. In Jmix CUBA we do not have checking for AbstractWindow.