Prevent flagging of deleted posts and don't show deleted posts in flagged post list (#3846)

store/sql_post_store.go

@@ -149,7 +149,7 @@ func (s SqlPostStore) GetFlaggedPosts(userId string, offset int, limit int) Stor
 		pl := &model.PostList{}
 
 		var posts []*model.Post
-		if _, err := s.GetReplica().Select(&posts, "SELECT * FROM Posts WHERE Id IN (SELECT Name FROM Preferences WHERE UserId = :UserId AND Category = :Category) ORDER BY CreateAt ASC LIMIT :Limit OFFSET :Offset", map[string]interface{}{"UserId": userId, "Category": model.PREFERENCE_CATEGORY_FLAGGED_POST, "Offset": offset, "Limit": limit}); err != nil {
+		if _, err := s.GetReplica().Select(&posts, "SELECT * FROM Posts WHERE Id IN (SELECT Name FROM Preferences WHERE UserId = :UserId AND Category = :Category) AND DeleteAt = 0 ORDER BY CreateAt ASC LIMIT :Limit OFFSET :Offset", map[string]interface{}{"UserId": userId, "Category": model.PREFERENCE_CATEGORY_FLAGGED_POST, "Offset": offset, "Limit": limit}); err != nil {
 			result.Err = model.NewLocAppError("SqlPostStore.GetFlaggedPosts", "store.sql_post.get_flagged_posts.app_error", nil, err.Error())
 		} else {
 			for _, post := range posts {