bug in evaluating a ring map on a complex

```m2
i1 : R = QQ[x,y,z];

i2 : C = complex coker vars R;

i3 : f = map(R, R, {0,0,0});

o3 : RingMap R <-- R

i4 : f C
stdio:4:1:(3): error: ring map applied to module with relations: use '**' or 'tensor' instead
```