There wasn’t much to celebrate at Party City this week, as the New Jersey-based retailer filed Chapter 11 bankruptcy after years of failing fortunes. Even before the pandemic, Party City was struggling for market share as shoppers began migrating to dollar stores, Five Below, Amazon, Target and Spirit Halloween. Then came two years of canceled festivities, plus a worldwide helium shortage that made it difficult to fill up all those party balloons. Party City currently operates about 800 stores, including one on Rockville Pike. No word yet on which locations might close.