BEIJING (Reuters) - China has no problem overcoming the middle-income trap, a senior economic official said on Thursday, referring to the situation in which economies risk stagnation at middle-income levels and fail to graduate into the ranks of advanced economies. Lou Jiwei, the chairman of the national council for the social security fund, was speaking on the sidelines of the 19th China Communist Party Congress. He previously served as the Minister of Finance until being replaced and named to head the social security fund last November.  