Improve URL extraction

[youtube-dl] / youtube_dl / extractor / frontendmasters.py

diff --git a/youtube_dl/extractor/frontendmasters.py b/youtube_dl/extractor/frontendmasters.py
index 770db46d0d63a0bdebea2d362850155b55044d93..cb57ba007fd61683630ea6cf2dd2d4d15d01ecc4 100644 (file)
--- a/youtube_dl/extractor/frontendmasters.py
+++ b/youtube_dl/extractor/frontendmasters.py
@@ -11,6 +11,7 @@ from ..compat import (
 from ..utils import (
     ExtractorError,
     parse_duration,
+    url_or_none,
     urlencode_postdata,
 )
 
@@ -80,7 +81,7 @@ class FrontendMastersPageBaseIE(FrontendMastersBaseIE):
         chapters = []
         lesson_elements = course.get('lessonElements')
         if isinstance(lesson_elements, list):
-            chapters = [e for e in lesson_elements if isinstance(e, compat_str)]
+            chapters = [url_or_none(e) for e in lesson_elements if url_or_none(e)]
         return chapters
 
     @staticmethod