Bug 455556: output an empty string when PR_FormatTime fails.  The patch is contributed by Julien Pierre <julien.pierre.boogz@sun.com>.  r=wtc.
Bug 455556: output an empty string when PR_FormatTime fails.  The patch is
contributed by Julien Pierre <julien.pierre.boogz@sun.com>.  r=wtc.

makotokato/nsprpub,makotokato/nsprpub,makotokato/nsprpub,makotokato/nsprpub,makotokato/nsprpub