Toronto - A city police officer was charged yesterday with assault in the videotapedbeating of a landed Somali immigrant in a case that could have resulted in the man’s deportation. The fee is the latest stain on the reputation of the city’s police force, which has been stung recently by accusations of corruption and racialprofiling.Const. Roy Preston, who had been on the force for two years at the time of the incident, appears in court on July 12.