The CW is making a casting change on its newly picked up drama series In the Dark, from CBS TV Studios and Ben Stiller's Red Hour Films. Austin Nichols, who co-starred in the pilot, is leaving; his role, Dean, will be recast. Written by Corinne Kingsbury and directed by Michael Showalter, In the Dark centers on Murphy (Perry Mattfeld), a flawed and irreverent young woman who just happens to be blind and is the only "witness" to the murder of her drug-dealing friend…