[YouTube] Cannot get contents of some auto-generated channels

Like:

Music: https://www.youtube.com/channel/UC-9-kyTW8ZkZNDHQJ6FgpwQ

Gaming: https://www.youtube.com/gaming

for Music channel: there are just empty relatedItems

for Gaming channel, here is the log:

2021-04-14 00:21:05.691 24560-24694/com.example.app W/System.err: org.schabi.newpipe.extractor.exceptions.ContentNotAvailableException: Not found ("404 ")
2021-04-14 00:21:05.692 24560-24694/com.example.app W/System.err:     at org.schabi.newpipe.extractor.services.youtube.YoutubeParsingHelper.getValidJsonResponseBody(YoutubeParsingHelper.java:602)
2021-04-14 00:21:05.692 24560-24694/com.example.app W/System.err:     at org.schabi.newpipe.extractor.services.youtube.YoutubeParsingHelper.getJsonResponse(YoutubeParsingHelper.java:662)
2021-04-14 00:21:05.692 24560-24694/com.example.app W/System.err:     at org.schabi.newpipe.extractor.services.youtube.extractors.YoutubeChannelExtractor.onFetchPage(YoutubeChannelExtractor.java:85)
2021-04-14 00:21:05.692 24560-24694/com.example.app W/System.err:     at org.schabi.newpipe.extractor.Extractor.fetchPage(Extractor.java:54)
2021-04-14 00:21:05.692 24560-24694/com.example.app W/System.err:     at org.schabi.newpipe.extractor.channel.ChannelInfo.getInfo(ChannelInfo.java:47)
2021-04-14 00:21:05.692 24560-24694/com.example.app W/System.err:     at com.example.app.v2.MainV2Act$onCreate$7.invoke(MainV2Act.kt:203)
2021-04-14 00:21:05.692 24560-24694/com.example.app W/System.err:     at com.example.app.v2.MainV2Act$onCreate$7.invoke(MainV2Act.kt:37)
2021-04-14 00:21:05.692 24560-24694/com.example.app W/System.err:     at org.jetbrains.anko.AsyncKt$doAsync$1.invoke(Async.kt:143)
2021-04-14 00:21:05.692 24560-24694/com.example.app W/System.err:     at org.jetbrains.anko.AsyncKt$doAsync$1.invoke(Unknown Source:0)
2021-04-14 00:21:05.693 24560-24694/com.example.app W/System.err:     at org.jetbrains.anko.AsyncKt$sam$java_util_concurrent_Callable$0.call(Unknown Source:2)
2021-04-14 00:21:05.693 24560-24694/com.example.app W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:266)
2021-04-14 00:21:05.693 24560-24694/com.example.app W/System.err:     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:301)
2021-04-14 00:21:05.693 24560-24694/com.example.app W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
2021-04-14 00:21:05.693 24560-24694/com.example.app W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
2021-04-14 00:21:05.693 24560-24694/com.example.app W/System.err:     at java.lang.Thread.run(Thread.java:923)

Start by reproducing the Music and Gaming channel URLs and read YoutubeChannelExtractor.java, especially the failing call path through YoutubeParsingHelper.java. Confirm how the empty relatedItems and 404 response are handled; done means the affected auto-generated channels expose their contents successfully.