That is more than likely a modification. Something that I might have done to mine but I still have mine.
I would suggest that you follow the advice of a few of the other sage repliers. Get a new vent created since you will need the vent for the fridge to function properly. The fridge needs to draw in air through the lower vent and exit at least at the top of the fridge opening. Most upper vents were half way up the wall above the fridge.
The lovely thing about fibreglass eggs is the fact that you can also create something out of fibreglass to accommodate a new vent cover. Allows for rounded corners. I did this to accommodate a larger fridge in our Boler.