Subscriptions: Fix Nil assertion failed (#3793)

src/invidious/channels/channels.cr

@@ -159,12 +159,18 @@ def fetch_channel(ucid, pull_all_videos : Bool)
   LOGGER.debug("fetch_channel: #{ucid}")
   LOGGER.trace("fetch_channel: #{ucid} : pull_all_videos = #{pull_all_videos}")
 
+  namespaces = {
+    "yt"      => "http://www.youtube.com/xml/schemas/2015",
+    "media"   => "http://search.yahoo.com/mrss/",
+    "default" => "http://www.w3.org/2005/Atom",
+  }
+
   LOGGER.trace("fetch_channel: #{ucid} : Downloading RSS feed")
   rss = YT_POOL.client &.get("/feeds/videos.xml?channel_id=#{ucid}").body
   LOGGER.trace("fetch_channel: #{ucid} : Parsing RSS feed")
-  rss = XML.parse_html(rss)
+  rss = XML.parse(rss)
 
-  author = rss.xpath_node(%q(//feed/title))
+  author = rss.xpath_node("//default:feed/default:title", namespaces)
   if !author
     raise InfoException.new("Deleted or invalid channel")
   end
@@ -192,15 +198,23 @@ def fetch_channel(ucid, pull_all_videos : Bool)
   videos, continuation = IV::Channel::Tabs.get_videos(channel)
 
   LOGGER.trace("fetch_channel: #{ucid} : Extracting videos from channel RSS feed")
-  rss.xpath_nodes("//feed/entry").each do |entry|
-    video_id = entry.xpath_node("videoid").not_nil!.content
-    title = entry.xpath_node("title").not_nil!.content
-    published = Time.parse_rfc3339(entry.xpath_node("published").not_nil!.content)
-    updated = Time.parse_rfc3339(entry.xpath_node("updated").not_nil!.content)
-    author = entry.xpath_node("author/name").not_nil!.content
-    ucid = entry.xpath_node("channelid").not_nil!.content
-    views = entry.xpath_node("group/community/statistics").try &.["views"]?.try &.to_i64?
-    views ||= 0_i64
+  rss.xpath_nodes("//default:feed/default:entry", namespaces).each do |entry|
+    video_id = entry.xpath_node("yt:videoId", namespaces).not_nil!.content
+    title = entry.xpath_node("default:title", namespaces).not_nil!.content
+
+    published = Time.parse_rfc3339(
+      entry.xpath_node("default:published", namespaces).not_nil!.content
+    )
+    updated = Time.parse_rfc3339(
+      entry.xpath_node("default:updated", namespaces).not_nil!.content
+    )
+
+    author = entry.xpath_node("default:author/default:name", namespaces).not_nil!.content
+    ucid = entry.xpath_node("yt:channelId", namespaces).not_nil!.content
+
+    views = entry
+      .xpath_node("media:group/media:community/media:statistics", namespaces)
+      .try &.["views"]?.try &.to_i64? || 0_i64
 
     channel_video = videos
       .select(SearchVideo)