valgrind errors in FORMapart tests

[jodavies]

On this branch https://github.com/jodavies/form/tree/ci-formapart I have integrated the FORMapart tests into the CI.

Some of the tests fail under valgrind with

==7113== Thread 3:
==7113== Conditional jump or move depends on uninitialised value(s)
==7113==    at 0x295AC3: CheckWild (wildcard.c:1876)
==7113==    by 0x28AB5F: RunReplace (transform.c:1624)
==7113==    by 0x2918E6: RunTransform (transform.c:782)
==7113==    by 0x2317DA: Generator (proces.c:3874)
==7113==    by 0x23276B: Generator (proces.c:4245)
==7113==    by 0x23209A: Generator (proces.c:4075)
==7113==    by 0x23276B: Generator (proces.c:4245)
==7113==    by 0x23276B: Generator (proces.c:4245)
==7113==    by 0x23276B: Generator (proces.c:4245)
==7113==    by 0x23276B: Generator (proces.c:4245)
==7113==    by 0x23276B: Generator (proces.c:4245)
==7113==    by 0x19A50E: SymGen (function.c:616)

[tueda]

The following simplified example almost always gives the Valgrind error with tvorm -w1:

CF f;
S x;
L F = f(2*x);
id f(x?) = f(x);
transform f,replace(1,1)=(xarg_,xarg_);
.end

==1229906== Thread 2:
==1229906== Conditional jump or move depends on uninitialised value(s)
==1229906==    at 0x418E136: CheckWild (wildcard.c:1876)
==1229906==    by 0x41828B9: RunReplace (transform.c:1624)
==1229906==    by 0x4189C6F: RunTransform (transform.c:782)
==1229906==    by 0x4126586: Generator (proces.c:3874)
==1229906==    by 0x4127531: Generator (proces.c:4245)
==1229906==    by 0x4126E77: Generator (proces.c:4075)
==1229906==    by 0x4127531: Generator (proces.c:4245)
==1229906==    by 0x41A4ED0: RunThread (threads.c:1423)
==1229906==    by 0x5E6E15D: start_thread (in /home/linuxbrew/.linuxbrew/Cellar/glibc/2.39/lib/libc.so.6)
==1229906==    by 0x5EE4A5F: clone (in /home/linuxbrew/.linuxbrew/Cellar/glibc/2.39/lib/libc.so.6)