Initialise the unit element in new_CRing

[pjbruin]

Reported by Markus Wageringel in #29247 comment:14:

sage: R.<x,y,z> = QQ[]
sage: from sage.libs.singular.function_factory import ff
sage: W = ff.ring(ff.ringlist(R), ring=R)
sage: C = sage.rings.polynomial.plural.new_CRing(W, R.base_ring())
sage: C.one()   # should be 1
0

CC: @mwageringel @tscrim

Component: coercion

Author: Peter Bruin

Branch/Commit: 799cf55

Reviewer: Travis Scrimshaw, Markus Wageringel

Issue created by migration from https://trac.sagemath.org/ticket/29311

[pjbruin]

Branch: u/pbruin/29311-new_CRing

[pjbruin]

Commit: cd3524d

[sagetrac-git]

Changed commit from cd3524d to 799cf55

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

799cf55

Trac 29311: initialise the unit element in new_CRing

[mwageringel]

comment:3

Thank you for fixing this so quickly. I can confirm that this also resolves the problem that came up in #25993.

I will add Travis to the reviewers, as he was positive about this approach.

[mwageringel]

Reviewer: Travis Scrimshaw, Markus Wageringel

[vbraun]

Changed branch from u/pbruin/29311-new_CRing to 799cf55