segfault with pca without -d:danger or -d:release
I am getting a segfault with pca, but only when built without release and without danger.

with gdb, I see:
```
Thread 16 "somalier" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fff9c7b1700 (LWP 4913)]
nimFrame (s=0x7fff9c7b0690) at /home/brentp/.cache/nim/somalier_d/@m..@s..@s..@s.nimble@spkgs@sarraymancer-@hhead@stensor@soperators_blas_l1.nim.c:359
359			(*s).calldepth = (NI16)((*framePtr__HRfVMH3jYeBJz6Q6X9b6Ptw).calldepth + ((NI16) 1));
(gdb) bt
#0  nimFrame (s=0x7fff9c7b0690) at /home/brentp/.cache/nim/somalier_d/@m..@s..@s..@s.nimble@spkgs@sarraymancer-@hhead@stensor@soperators_blas_l1.nim.c:359
#1  check_size__A1o8pjA8sSUzNxmn3BamlAp_checks (a=a@entry=0x7ffffffdf2c0, b=b@entry=0x7fff9c7b0cd0)
    at /home/brentp/.cache/nim/somalier_d/@m..@s..@s..@s.nimble@spkgs@sarraymancer-@hhead@stensor@soperators_blas_l1.nim.c:1717
#2  0x00005555556a2045 in pluseq___bwzvgAiJVLEdRKerBiTtXA._omp_fn.0 ()
    at /home/brentp/.cache/nim/somalier_d/@m..@s..@s..@s.nimble@spkgs@sarraymancer-@hhead@stensor@soperators_blas_l1.nim.c:1893
#3  0x00007ffff7e32e96 in GOMP_parallel () from /lib/x86_64-linux-gnu/libgomp.so.1
#4  0x00005555556a8f7b in pluseq___bwzvgAiJVLEdRKerBiTtXA (a=0x7ffffffdf2c0, b=b@entry=0x7fff9c7b0cd0)
    at /home/brentp/.cache/nim/somalier_d/@m..@s..@s..@s.nimble@spkgs@sarraymancer-@hhead@stensor@soperators_blas_l1.nim.c:1848
#5  0x00005555556de762 in sum__Y49asUKPCVhBx9cvcl0dU9blA._omp_fn.0 () at /home/brentp/.cache/nim/somalier_d/@m..@s..@s..@s.nimble@spkgs@sarraymancer-@hhead@stensor@saggregate.nim.c:1184
#6  0x00007ffff7e3c31e in ?? () from /lib/x86_64-linux-gnu/libgomp.so.1
#7  0x00007ffff7e07669 in start_thread (arg=<optimized out>) at pthread_create.c:479
#8  0x00007ffff7d2f323 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95
```
if that's not helpful I can try to get means to recreate (from [somalier](https://github.com/brentp/somalier))