 Shares of Shake Shack Inc. SHAK, -4.55 headed more than 6 lower in the extended session Thursday after the fast-casual restaurant reported a fourth-quarter loss that was greater than Wall Street expected and said the timing of a full recovery is still uncertain. Shake Shack said it lost 9.7 million, or 25 cents a share, in the fourth quarter, compared with a loss of 19.4 million, or 50 cents a share, in the year-ago period. 