#14 共通のサムネとタイトルの取得は完成

frontend/src/pages/PostNewPage.tsx

@@ -37,10 +37,12 @@ const PostNewPage = () => {
 
   const handleSubmit = () => {
     const formData = new FormData ()
-    formData.append ('title', title || null)
+    if (title)
+      formData.append ('title', title)
     formData.append ('url', url)
     formData.append ('tags', JSON.stringify (tagIds))
-    formData.append ('thumbnail', thumbnailAutoFlg ? null : thumbnailFile)
+    if (!(thumbnailAutoFlg) && thumbnailFile)
+      formData.append ('thumbnail', thumbnailFile)
 
     void (axios.post (`${ API_BASE_URL }/posts`, formData, { headers: {
               'Content-Type':     'multipart/form-data',