:recycle: add back skipping seen title insert

vue-theme/src/store/modules/arrangements.js

@@ -47,6 +47,7 @@ const _arrangeByAlpha = (postsList, seenTitles) => {
     const flatPacked = []
     
     const storeTitle = letter => {
+        if(seenTitles.includes(letter)) return
         flatPacked.push({ slug: letter, title: letter, inbetween: true })
         seenTitles.push(letter)
     }