fix(SPA): 修复头像为空时会报错的问题

Author: mutoe

resources/spa/src/components/form/FormAvatarItem.vue

@@ -39,7 +39,7 @@ export default {
   },
   data () {
     return {
-      avatar: this.$props.value.url,
+      avatar: (this.$props.value || {}).url,
     }
   },
   methods: {