fixed compiler error in VariableSeq.
fixed compiler error in VariableSeq.

pogren-oracle/factorie,Craigacp/factorie,hlin117/factorie,joprice/factorie,digitalreasoning/factorie-scala-210,strubell/factorie,factorie/factorie,zxsted/factorie,melisabok/factorie,asubbaswamy/factorie,patverga/factorie,malcolmgreaves/factorie