[14358] Fix NPE in ContextService#createNamedContext

bundles/ch.elexis.core.ui/src/ch/elexis/core/ui/services/internal/ContextService.java

@@ -104,6 +104,7 @@ public class ContextService implements IContextService, EventHandler {
 	@Activate
 	public void activate(){
 		root = new Context();
+		contexts = new ConcurrentHashMap<>();
 		eventDispatcherListener = new SelectionEventDispatcherListener();
 		reloadEventDispatcherListener = new ReloadEventDispatcherListener();
 		lockingEventDispatcherListener = new LockingEventDispatcherListener();