広場投稿追加画面の刷新 (#399) (#413)

Reviewed-on: http://git.miteruzo.com/miteruzo/btrc-hub/pulls/413
Co-authored-by: miteruzo <miteruzo@naver.com>
Co-committed-by: miteruzo <miteruzo@naver.com>

frontend/src/pages/users/SettingPage.tsx

@@ -1197,13 +1197,9 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
   }, [hasUnsavedThemeChanges, savedThemeSlots])
 
   useEffect (() => {
-    registerUnsavedChangesSource ({
-	dirty: hasPageUnsavedChanges,
-	discard: discardAllDirtyChanges })
-
-    return () => {
-      registerUnsavedChangesSource (null)
-    }
+    return registerUnsavedChangesSource ({
+        dirty: hasPageUnsavedChanges,
+        discard: discardAllDirtyChanges })
   }, [discardAllDirtyChanges, hasPageUnsavedChanges, registerUnsavedChangesSource])
 
   useKeyboardShortcuts ({