merge #6865: [lofter] improve error handling

- Add 'NotFoundError' when the lofter blog returns a 404
- Stop extractor if the blog is empty, because this returns
  {offset: -1} in the data which previously infinity-looped
  the extractor.
- Prevent errors when the blog is locked, the posts in
  self.posts() are None

gallery_dl/extractor/lofter.py

@@ -23,6 +23,8 @@ class LofterExtractor(Extractor):
 
     def items(self):
         for post in self.posts():
+            if post is None:
+                continue
             if "post" in post:
                 post = post["post"]
 
@@ -129,6 +131,9 @@ class LofterAPI():
             url, method="POST", params=params, data=data)
         info = response.json()
 
+        if info["meta"]["status"] == 4200:
+            raise exception.NotFoundError("blog")
+
         if info["meta"]["status"] != 200:
             self.extractor.log.debug("Server response: %s", info)
             raise exception.StopExtraction("API request failed")
@@ -142,6 +147,9 @@ class LofterAPI():
 
             yield from posts
 
+            if data["offset"] < 0:
+                break
+
             if params["offset"] + len(posts) < data["offset"]:
                 break
             params["offset"] = data["offset"]