A segfault in the Linux cp313t CI job

[rgommers]

This is the first crash in the free-threaded CI job that I think I've seen. It seems to be in test_wpnd.py, from this log:

 ../tests/test_wavelet.py ......                                          [ 97%]
../tests/test_wp.py ...........                                          [ 98%]
../tests/test_wp2d.py ..........                                         [ 99%]
/home/runner/work/_temp/2c1e28e9-b13b-44fa-9ae2-cf26dcc4d062.sh: line 3:  2823 Segmentation fault      (core dumped) pytest --pyargs pywt
../tests/test_wpnd.py ....

No more details, so for now just filing an issue to keep track of this.