when MP4 init file is missing, the error msg is obtuse

[mikedo]

When processing an MP4 file list, if an init file (filename with "init" in it) is omitted, the error message is: "error XML parsing error: not well-formed (invalid token): line 1, column 0", which appears as if it is processing a text (xml) file. It would be better if the message was something like "required init file is missing".