Wrong result for multivariate polynomial evaluation

<div id="comment:0"></div>

Example:

```sage
sage: R.<x,y> = Zmod(9)[]
sage: f = x^2 * y
sage: f(3, 1)
1
```

Upstream: **Fixed upstream, in a later stable release.**

CC:  @malb

Component: **algebra**

_Issue created by migration from https://trac.sagemath.org/ticket/34417_

