fixed little bug in layoutengine

lib/network/modules/LayoutEngine.js

@@ -1,3 +1,5 @@
+'use strict'
+
 var util = require('../../util');
 
 class LayoutEngine {
@@ -78,14 +80,14 @@ class LayoutEngine {
         allOptions.physics = {solver: 'hierarchicalRepulsion'};
         this.optionsBackup.physics = {solver:'barnesHut'};
       }
-      else if (typeof options.physics === 'object') {
+      else if (typeof allOptions.physics === 'object') {
         this.optionsBackup.physics = {solver:'barnesHut'};
-        if (options.physics.solver !== undefined) {
+        if (allOptions.physics.solver !== undefined) {
           this.optionsBackup.physics = {solver:options.physics.solver};
         }
         allOptions.physics['solver'] = 'hierarchicalRepulsion';
       }
-      else if (options.physics !== false) {
+      else if (allOptions.physics !== false) {
         this.optionsBackup.physics = {solver:'barnesHut'};
         allOptions.physics['solver'] = 'hierarchicalRepulsion';
       }