[bugfix] Toast: ssr error (#1910)

packages/dialog/index.js

@@ -1,5 +1,6 @@
 import Vue from 'vue';
 import VanDialog from './Dialog';
+import { isServer } from '../utils';
 
 let instance;
 
@@ -16,6 +17,11 @@ const initInstance = () => {
 };
 
 const Dialog = options => {
+  /* istanbul ignore if */
+  if (isServer) {
+    return Promise.resolve();
+  }
+
   return new Promise((resolve, reject) => {
     if (!instance) {
       initInstance();