Segmentation fault when reference FASTA does not exist or has wrong format

[marcelm]

The program exits with a segfault when the reference FASTA file does not exist:

$ strobealign ref.fasta dummy.fasta
...
Unique strobemers: 1
Total time generating flat vector: 3.2896e-05 s

Flat vector size: 0
Segmentation fault (core dumped)

The same happens when a compressed FASTA (.gz) was provided (even if it exists).