A lot of manufacturers are not putting gutters on the awning areas (side) of their trailers. Saves them money and they reason that the awning will take care of rain, etc.
One trick I learned a lot of years ago concerning the A/C drainage is to make the trailer 1/2" low on the streetside and 1/2" high in the front when leveling up. Even 3/4" if that's as close as I can get. Those "unlevel" figures aren't enough to be noticeable inside and won't affect the refrigerator, but, it will cause the A/C condensate to drain off the streetside rear of the trailer...that's the most "unused" area around the trailer and a puddle back there is a non-issue.
You could try to install an aftermarket gutter, but, that just introduces more "leak" points along that whole edge and could be more trouble and potential damage than it would be worth.