update LibraryTree with MapZoom

src/store/modules/library.js

@@ -177,7 +177,7 @@ export default {
       })
     },
 
-    activeNodes: (state) => {
+    activeNodes: state => {
       if (!state.nodebook) return []
       return state.nodebook.reduce((acc, ids) => [...acc, ...ids], [])
     },
@@ -218,8 +218,7 @@ export default {
     },
 
     nodeTree: (state, rootState) => {
-      if (state.nodeDepartId === undefined) return
-      return state.trees[state.nodeDepartId]
+      return state.trees[state.nodeDepartId] || { nodes: [], links: [] }
     }
   }
 }