code: function onerror(er) {
  	    debug('onerror', er);
  	    unpipe();
  	    dest.removeListener('error', onerror);
  	    if (listenerCount$1(dest, 'error') === 0) dest.emit('error', er);
  	  }
docs: if the dest has an error, then stop piping into it. however, don't suppress the throwing behavior for this.