Fix some UI bug on test module (#341)

1. The service test page will throw undefined exception in console if the "service" parameter in url is null.
2. Keep the style of service test page consistent with other pages
diff --git a/dubbo-admin-ui/src/components/test/ServiceTest.vue b/dubbo-admin-ui/src/components/test/ServiceTest.vue
index 7902526..95cff5e 100644
--- a/dubbo-admin-ui/src/components/test/ServiceTest.vue
+++ b/dubbo-admin-ui/src/components/test/ServiceTest.vue
@@ -20,8 +20,7 @@
       <v-flex lg12>
         <breadcrumb title="serviceTest" :items="breads"></breadcrumb>
       </v-flex>
-      <v-layout row wrap>
-        <v-flex lg12>
+      <v-flex lg12>
           <v-card flat color="transparent">
             <v-card-text>
               <v-form>
@@ -45,29 +44,37 @@
             </v-card-text>
           </v-card>
         </v-flex>
-      </v-layout>
       <v-flex xs12>
-        <h3>{{$t('methods')}}</h3>
-      </v-flex>
-      <v-flex xs12>
-        <v-data-table :headers="headers" :items="methods" hide-actions class="elevation-1">
-          <template slot="items" slot-scope="props">
-            <td>{{ props.item.name }}</td>
-            <td><v-chip xs v-for="(type, index) in props.item.parameterTypes" :key="index" label>{{ type }}</v-chip></td>
-            <td><v-chip label>{{ props.item.returnType }}</v-chip></td>
-            <td class="text-xs-right">
-              <v-tooltip bottom>
-                <v-btn
-                  fab dark small color="blue" slot="activator"
-                  :href="getHref(props.item.application, props.item.service, props.item.signature)"
-                >
-                  <v-icon>edit</v-icon>
-                </v-btn>
-                <span>{{$t('test')}}</span>
-              </v-tooltip>
-            </td>
-          </template>
-        </v-data-table>
+        <v-card>
+          <v-toolbar flat color="transparent" class="elevation-0">
+            <v-toolbar-title><span class="headline">{{$t('methods')}}</span></v-toolbar-title>
+            <v-spacer></v-spacer>
+          </v-toolbar>
+          <v-card-text class="pa-0">
+            <v-data-table :headers="headers" :items="methods" hide-actions class="elevation-1">
+              <template slot="items" slot-scope="props">
+                <td>{{ props.item.name }}</td>
+                <td>
+                  <v-chip xs v-for="(type, index) in props.item.parameterTypes" :key="index" label>{{ type }}</v-chip>
+                </td>
+                <td>
+                  <v-chip label>{{ props.item.returnType }}</v-chip>
+                </td>
+                <td class="text-xs-right">
+                  <v-tooltip bottom>
+                    <v-btn
+                      fab dark small color="blue" slot="activator"
+                      :href="getHref(props.item.application, props.item.service, props.item.signature)"
+                    >
+                      <v-icon>edit</v-icon>
+                    </v-btn>
+                    <span>{{$t('test')}}</span>
+                  </v-tooltip>
+                </td>
+              </template>
+            </v-data-table>
+          </v-card-text>
+        </v-card>
       </v-flex>
     </v-layout>
   </v-container>
@@ -231,7 +238,7 @@
     mounted () {
       this.$store.dispatch('loadServiceItems')
       let query = this.$route.query
-      this.filter = query['service']
+      this.filter = query['service'] || ''
       if ('group' in query) {
         this.filter = query['group'] + '/' + this.filter
       }
@@ -241,6 +248,7 @@
       if (this.filter) {
         this.search(this.filter.replace('/', '*'))
       }
+      this.setHeaders()
     }
   }
 </script>