Bear sightings are not that unusual in unincorporated Nevada County. But multiple reports have come in the last two weeks of a bear, often accompanied by a cub, wandering through downtown Grass Valley. The spate of calls began at around 10 a.m. Oct. 12, with multiple people calling Grass Valley Police to report the duo in the area of Harris and Eureka streets. Officers responded and searched for at least a half-hour without spotting the elusive ursines, said Capt. Rex Marks. Another bruin spotting was called in just before 1 a.m. the next day in the 800 block of East …