Disk cache crashes for exec()'d functions with `__module__=None`

"""[debug.py]

Run twice. First run compiles and caches. Second run loads cache and crashes.

  $ python debug.py    # first: compiles and caches — OK
  $ python debug.py    # second: loads cache — CRASH

Clean up with: rm -rf _numba_bug_cache
"""
import os, numba, numpy as np

cache_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "_numba_bug_cache")
src_file = os.path.join(cache_dir, "wrapper.py")

# Only create the file if it doesn't exist (preserve mtime for cache validity)
if not os.path.exists(src_file):
    os.makedirs(cache_dir, exist_ok=True)
    with open(src_file, "w") as fh:
        fh.write("def wrapper(*args): return _inner(*args)\n")

@numba.njit
def add_one(x):
    return x + 1

env = {"_inner": add_one}
# needs a __name__
exec(compile(open(src_file).read(), src_file, "exec"), env)
f = numba.njit(cache=True)(env["wrapper"])
print(f(np.array([1.0, 2.0, 3.0])))

Traceback (most recent call last):
  File "/home/ricardo/Documents/pytensor-tree1/debug_numba_fork.py", line 28, in <module>
    print(f(np.array([1.0, 2.0, 3.0])))
          ~^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ricardo/Documents/pytensor-tree1/.venv/lib64/python3.13/site-packages/numba/core/dispatcher.py", line 443, in _compile_for_args
    raise e
  File "/home/ricardo/Documents/pytensor-tree1/.venv/lib64/python3.13/site-packages/numba/core/dispatcher.py", line 376, in _compile_for_args
    return_val = self.compile(tuple(argtypes))
  File "/home/ricardo/Documents/pytensor-tree1/.venv/lib64/python3.13/site-packages/numba/core/dispatcher.py", line 889, in compile
    cres = self._cache.load_overload(sig, self.targetctx)
  File "/home/ricardo/Documents/pytensor-tree1/.venv/lib64/python3.13/site-packages/numba/core/caching.py", line 721, in load_overload
    return self._load_overload(sig, target_context)
           ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/home/ricardo/Documents/pytensor-tree1/.venv/lib64/python3.13/site-packages/numba/core/caching.py", line 728, in _load_overload
    data = self._cache_file.load(key)
  File "/home/ricardo/Documents/pytensor-tree1/.venv/lib64/python3.13/site-packages/numba/core/caching.py", line 576, in load
    return self._load_data(data_name)
           ~~~~~~~~~~~~~~~^^^^^^^^^^^
  File "/home/ricardo/Documents/pytensor-tree1/.venv/lib64/python3.13/site-packages/numba/core/caching.py", line 618, in _load_data
    tup = pickle.loads(data)
  File "/home/ricardo/Documents/pytensor-tree1/.venv/lib64/python3.13/site-packages/numba/core/environment.py", line 51, in _rebuild_env
    mod = importlib.import_module(modname)
  File "/usr/lib64/python3.13/importlib/__init__.py", line 80, in import_module
    if name.startswith('.'):
       ^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'startswith'