[youtube] Allow empty attribute values in description regex

youtube_dl/extractor/youtube.py

@@ -1326,9 +1326,9 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         if video_description:
             video_description = re.sub(r'''(?x)
                 <a\s+
-                    (?:[a-zA-Z-]+="[^"]+"\s+)*?
+                    (?:[a-zA-Z-]+="[^"]*"\s+)*?
                     (?:title|href)="([^"]+)"\s+
-                    (?:[a-zA-Z-]+="[^"]+"\s+)*?
+                    (?:[a-zA-Z-]+="[^"]*"\s+)*?
                     class="(?:yt-uix-redirect-link|yt-uix-sessionlink[^"]*)"[^>]*>
                 [^<]+\.{3}\s*
                 </a>