rm redundant check

pub/lib/expr.cpp

@@ -300,7 +300,5 @@ void CNode::tree_vec_val( vector<double> *ret, vector<double> *dret, int k, int
 RObj CNode::eval( string expr )
 {
     RNode T = user_xaxparse( expr.c_str() );
-    if( T->k_dependent() )
-        throw "Cannot evaluate '" + expr + "': missing context K";
     return T->tree_point_val();
 }