Tumbleweed Tuesday might be a thing of the past, but empty storefronts still proliferate in East Hampton Village during the off-season. This winter, however, the windows of at least one high-end Main Street clothing purveyor, Malia Mills, will not be papered over. The company has decided to make its empty space available to artists for a series of exhibitions, the first of which will open on Saturday with a reception from 5 to 7 p.m. It will feature the work of the East End artists Bastienne Schmidt, Almond Zigmund, Margaret Garrett, and Philippe Cheng.