[scrolller] fix exception for albums with missing media (#7428)

fixes regression introduced in a44ea6b3d9

gallery_dl/extractor/scrolller.py

@@ -56,7 +56,12 @@ class ScrolllerExtractor(Extractor):
 
         files = []
         for num, media in enumerate(album, 1):
-            src = max(media["mediaSources"], key=self._sort_key)
+            sources = media.get("mediaSources")
+            if not sources:
+                self.log.warning("%s/%s: Missing media file",
+                                 post.get("id"), num)
+                continue
+            src = max(sources, key=self._sort_key)
             src["num"] = num
             files.append(src)
         return files

gallery_dl/version.py

@@ -6,5 +6,5 @@
 # it under the terms of the GNU General Public License version 2 as
 # published by the Free Software Foundation.
 
-__version__ = "1.29.5"
+__version__ = "1.29.6-dev"
 __variant__ = None