Error when close screen with two Properties views

In WireframeSketcher 7.2.1 on macOS Sequoia 15.2, if I have two Properties views open and have selected a widget in an open screen, if I then close the screen, I get a "Problem Occurred" error dialog

with the following error message:

An error has occurred. See error log for more details.

Cannot invoke "org.eclipse.ui.part.IPageSite.getSelectionProvider()" because the return value of "com.wireframesketcher.ui.mh.getSite()" is null

Steps to reproduce:

1. Create a new Wireframe project.
2. Open the automatically created screen NewScreen.screen.
3. Drag a Button widget into the screen.
4. Save the screen.
5. In the Properties view, click the vertical ellipsis icon, and choose New Properties View.
6. Click the Button widget, and its properties should be displayed in the newly opened Properties view.
7. Click the X icon on the screen's tab to close the screen, which will result in the error dialog.

I'm not sure what the usefulness of being able to create more than one Properties view is, but it's allowed, and then this can happen.

Thank you for reporting this issue! I could reproduce it locally and will look into it.