fix(Appearance Settings): There is an issue with the preview page displaying the left side of the welcome message in the platform login settings.

Author: dataeaseShu

frontend/src/views/login/index.vue

@@ -24,7 +24,7 @@
           }}</span>
         </div>
         <div v-if="appearanceStore.getShowSlogan" class="welcome">
-          {{ appearanceStore.slogan || $t('common.intelligent_questioning_platform') }}
+          {{ appearanceStore.slogan ?? $t('common.intelligent_questioning_platform') }}
         </div>
         <div v-else class="welcome" style="height: 0"></div>
         <div class="login-form">

frontend/src/views/system/appearance/LoginPreview.vue

@@ -52,7 +52,7 @@
               </div>
             </div>
             <div v-if="isBtnShow(showSlogan)" class="login-welcome">
-              {{ pageSlogan || t('system.available_to_everyone') }}
+              {{ pageSlogan ?? t('common.intelligent_questioning_platform') }}
             </div>
             <div v-else class="login-welcome"></div>
           </div>