Check if genomes exists

[snayfach]

If there are no valid genomes provided, Maast should exit with informative error instead of proceeding to next step. In the example below I provided a directory of gzipped FASTA files and got the following error:

[Warning] Total number of genomes (0) < min. number of genomes required for effective SNP calling with MAF 0.01 (100)
[Warning] Skip tag genome selection, all genomes will be used
reference genome path:
[building mash sketch]: start
b''
b"mash: Relink /global/u1/s/snayfach/.conda/envs/maast/bin/../lib/./libgfortran.so.5' with /lib64/librt.so.1' for IFUNC symbol `clock_gettime'\nWriting to maast/100/temp/mash/100/mash_sketch.msh...\n"[calculating mash distance]: start

Error: the following returned non-zero status: 'mash dist -p 1 maast/100/temp/mash/100/mash_sketch.msh maast/100/temp/mash/100/mash_sketch.msh > maast/100/temp/mash/100/mash_dist.tsv ':

b"mash: Relink /global/u1/s/snayfach/.conda/envs/maast/bin/../lib/./libgfortran.so.5' with /lib64/librt.so.1' for IFUNC symbol `clock_gettime'\n/bin/sh: line 1: 10466 Floating point exceptionmash dist -p 1 maast/100/temp/mash/100/mash_sketch.msh maast/100/temp/mash/100/mash_sketch.msh > maast/100/temp/mash/100/mash_dist.tsv\n"

[snayfach]

Also, looks like you have an off-by one error:

[Warning] Total number of genomes (100) < min. number of genomes required for effective SNP calling with MAF 0.01 (100)

[zjshi]

Min genome number checking added.