Ignore error in marshaled data if Perforce file type is utf16

The value of "code" in marshaled data is often "error", which is
"CANNOT TRANSLATE" error message [1] with "p4 -G -x - print",
if Perforce file type is utf16. But the missing data will be handled properly
in the streamOneP4File method with "p4 print -o".

  [1]
  Internationalization Notes for P4D, the Perforce Server and Perforce
  client applications
  http://www.perforce.com/perforce/doc.current/user/i18nnotes.txt