one occasion less to crash

(on debug builds an assert is still possible)

src/scriptengines/qml/plasmoid/containmentinterface.cpp

@@ -91,6 +91,9 @@ ContainmentInterface::ContainmentInterface(DeclarativeAppletScript *parent, cons
 
     connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit,
             [=]() {
+                if (!containment()) {
+                    return;
+                }
                 disconnect(containment(), &Plasma::Containment::appletRemoved,
                 this, &ContainmentInterface::appletRemovedForward);
         });