Weak sales at Urban Ouftitters are a concern. Debt and weak free cash flow are even more of a concern.Urban Outfitters (URBN -10.66%) stock tumbled 10% through 10:10 a.m. ET Thursday morning, despite the company beating analyst forecasts for second-quarter sales and earnings last night.Heading into the results, analysts forecast the teen retailer would earn $1 per share on sales of$1.34 billion. In fact, profits were a superb $1.24 per share, and sales edged out the consensus estimate at$1.35 billion. Sal ...