fixed little bug in layoutengine and it's brother

lib/network/modules/LayoutEngine.js

@@ -83,7 +83,7 @@ class LayoutEngine {
       else if (typeof allOptions.physics === 'object') {
         this.optionsBackup.physics = {solver:'barnesHut'};
         if (allOptions.physics.solver !== undefined) {
-          this.optionsBackup.physics = {solver:options.physics.solver};
+          this.optionsBackup.physics = {solver:allOptions.physics.solver};
         }
         allOptions.physics['solver'] = 'hierarchicalRepulsion';
       }