fix openPageCreateModal and add logger

src/client/js/services/NavigationContainer.js

@@ -176,6 +176,10 @@ export default class NavigationContainer extends Container {
   }
 
   openPageCreateModal() {
+    if (this.appContainer.currentUser == null) {
+      logger.warn('Please login or signup to create page.');
+      return;
+    }
     this.setState({ isPageCreateModalShown: true });
   }