update npm modules, try to fix #40

Author: jogibear9988

lib/es5/dock-spawn-ts.js

@@ -15,7 +15,7 @@ export interface ILayoutEventListener {
     onChangeDialogPosition?(dockManager: DockManager, dialog: Dialog, x: number, y: number): void;
     onContainerResized?(dockManager: DockManager, dockContainer: IDockContainer): void;
     onTabChanged?(dockManager: DockManager, tabpage: TabPage): void;
-    onActivePanelChange?(dockManager: DockManager, panel: PanelContainer, previousPanel?: PanelContainer): void;
+    onActivePanelChange?(dockManager: DockManager, panel?: PanelContainer, previousPanel?: PanelContainer): void;
     /**
     * The Dock Manager notifies the listeners of layout changes so client containers that have
     * costly layout structures can detach and reattach themself to avoid reflow