Core: Set unit scheme when switching between unsaved documents

Fixes #17297

src/Gui/Application.cpp

@@ -1027,7 +1027,7 @@ void Application::slotActiveDocument(const App::Document& Doc)
         // Update the application to show the unit change
         ParameterGrp::handle hGrp = App::GetApplication().GetParameterGroupByPath(
             "User parameter:BaseApp/Preferences/Units");
-        if (Doc.FileName.getValue()[0] != '\0' && !hGrp->GetBool("IgnoreProjectSchema")) {
+        if (!hGrp->GetBool("IgnoreProjectSchema")) {
             int userSchema = Doc.UnitSystem.getValue();
             Base::UnitsApi::setSchema(static_cast<Base::UnitSystem>(userSchema));
             getMainWindow()->setUserSchema(userSchema);