channelName check failed, should be a non-empty string<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function addPrivilege() on null in /var/www/html/backend/agora/RtcTokenBuilder.php:47
Stack trace:
#0 /var/www/html/backend/agora/RtcTokenBuilder.php(28): RtcTokenBuilder::buildTokenWithUserAccount()
#1 /var/www/html/backend/generate_agora_token.php(17): RtcTokenBuilder::buildTokenWithUid()
#2 {main}
  thrown in <b>/var/www/html/backend/agora/RtcTokenBuilder.php</b> on line <b>47</b><br />