[twitter] improve twitpic extraction (fixes #1019)

- ignore twitpic.com/photos/… URLs
- ignore empty image URLs

CHANGELOG.md

@@ -1,5 +1,7 @@
 # Changelog
 
+## Unreleased
+
 ## 1.15.0 - 2020-09-20
 ### Additions
 - [deviantart] support watchers-only/paid deviations ([#995](https://github.com/mikf/gallery-dl/issues/995))

gallery_dl/extractor/twitter.py

@@ -110,12 +110,13 @@ class TwitterExtractor(Extractor):
         twitpics = []
         for url in tweet["entities"].get("urls", ()):
             url = url["expanded_url"]
-            if "//twitpic.com/" in url:
+            if "//twitpic.com/" in url and "/photos/" not in url:
                 response = self.request(url, fatal=False)
                 if response.status_code >= 400:
                     continue
                 url = text.extract(
                     response.text, 'name="twitter:image" value="', '"')[0]
+                if url:
                     twitpics.append({
                         "original_info": {},
                         "media_url"    : url,

gallery_dl/version.py

@@ -6,4 +6,4 @@
 # it under the terms of the GNU General Public License version 2 as
 # published by the Free Software Foundation.
 
-__version__ = "1.15.0"
+__version__ = "1.15.1-dev"