fix: sub enable warning

web/html/form/client.html

@@ -44,7 +44,7 @@
             <a-select-option v-for="key in USERS_SECURITY" :value="key">[[ key ]]</a-select-option>
         </a-select>
     </a-form-item>
-    <a-form-item v-if="client.email && app.subSettings.enable">
+    <a-form-item v-if="client.email && app.subSettings?.enable">
         <template slot="label">
             <a-tooltip>
                 <template slot="title">

web/html/modals/client_bulk_modal.html

@@ -39,7 +39,7 @@
                 <a-select-option v-for="key in TLS_FLOW_CONTROL" :value="key">[[ key ]]</a-select-option>
             </a-select>
         </a-form-item>
-        <a-form-item v-if="app.subSettings.enable">
+        <a-form-item v-if="app.subSettings?.enable">
             <template slot="label">
                 <a-tooltip>
                     <template slot="title">

web/html/modals/qrcode_modal.html

@@ -21,7 +21,7 @@
     </a-space>
   </template>
   <tr-qr-modal class="qr-modal">
-    <template v-if="app.subSettings.enable && qrModal.subId">
+    <template v-if="app.subSettings?.enable && qrModal.subId">
       <tr-qr-box class="qr-box">
         <a-tag color="purple" class="qr-tag"><span>{{ i18n "pages.settings.subSettings"}}</span></a-tag>
         <tr-qr-bg class="qr-bg-sub">