WHATCOM — The median sales price of a Bellingham home surpassed $400,000 in a quarter for the first time, according to a local real-estate broker. Bellingham’s median sales price was $405,242 in the recently completed third quarter of 2017, up 9.3 percent from 2016’s third quarter, according to Troy Muljat, managing broker of Bellingham-based Muljat…