Photo by staceyviera If your lunchtime routine often includes the Potbelly Sandwich Works location at 1900 L St. NW, you may have run into some trouble snagging that meatball sub on wheat bread today. The restaurant was briefly evacuated in the middle of the lunch rush on Monday due to customer complaints of an apparent mild irritant in the air. D.C. Fire/EMS spokesperson Pete Piringer said hazmat tests for possible air toxins inside the…