XLR PR5E/VS

When I forst got my Epiphone PR5E/VS , I  realizes the battery test wouldn't work without a phono plug plugged into it.
I assumed this was to save on batteries.
Lately I've been playing in a band and realized the XLR output jack , sent to a mixer , wouldn't work unless a phono jack was plugged in as well .
No problem I use a stage amp  as well .
I've emailed the  Canadian Epiphone Rep with no reply , anyone have the same occurance or advise.