Error:
err:XPTY0004: Need context item that is a node to get root element
Possible backtrace:
  $000000000056AA6F: perhaps TXQTermTryCatch + 81151 ? but unlikely
  $0000000000549472: perhaps TXQTermBinaryOp + 4722 ? but unlikely

Call xidel with --trace-stack to get an actual backtrace