Our build displays several warnings like

warning: sage/libs/ntl/ntl_ZZ.pyx:274:23: local variable 'ans' referenced before assignment

for variables that are passed by reference to a C function that overwrites them (meaning that there is no real bug). Here we fix a few easy ones by initializing the variable.

Component: build

Author: Michael Orlitzky

Branch/Commit: 93f2e90

Reviewer: Markus Wageringel, Marc Mezzarobba

Issue created by migration from https://trac.sagemath.org/ticket/33176