`optimizer_symbols.c`: `make_bottom` NULL deref when arena full

[A0su]

Bug report

Bug description:

optimizer_symbols.c: make_bottom NULL deref when arena full

sym_new(ctx) at line 1535 can return NULL when the type arena is full. Result immediately dereferenced without check. Every other sym_new call site checks for NULL.

This is a sub-issue of #146102 with gist details

CPython versions tested on:

CPython main branch

Operating systems tested on:

Windows

Linked PRs

• gh-146388: Add null check for sym_new(ctx) in make_bottom #146389