perf[i18n]: refine generateTitle function

src/utils/i18n.js

 // translate router.meta.title, be used in breadcrumb sidebar tagsview
 export function generateTitle(title) {
-  return this.$t('route.' + title) // $t :this method from vue-i18n, inject in @/lang/index.js
+  const hasKey = this.$te('route.' + title)
+  const translatedTitle = this.$t('route.' + title) // $t :this method from vue-i18n, inject in @/lang/index.js
+
+  if (hasKey) {
+    return translatedTitle
+  }
+  return title
 }