💚 Fix pytest error

[evanroyrees]

pytest CI is currently failing due to test in tests/unit_tests/test_unclustered_recruitment.py::test_main.

This test failure currently exists in the dev branch as the autometa/binning/unclustered_recruitment.py script was unaltered in the corresponding PR #324 (which only changes autometa/binning/large_data_mode.py)

(example here: https://github.com/KwanLab/Autometa/actions/runs/4994350221/jobs/8945027824#step:5:307)

=========================== short test summary info ============================
FAILED tests/unit_tests/test_unclustered_recruitment.py::test_main - ValueError: attempt to get argmax of an empty sequence
======= 1 failed, 99 passed, 12 skipped, 8 warnings in 104.68s (0:01:44) =======
Using no_dims = 2, perplexity = 0.333333, theta = 0.500000, seed=-484417574
Computing input similarities...
Perplexity should be lower than K!
Building tree...
 - point 0 of 5
Done in 0.00 seconds (sparsity = 0.000000)!
Learning embedding...
Fitting performed in 0.00 seconds.
Perplexity should be lower than K!
Perplexity should be lower than K!
Perplexity should be lower than K!
Perplexity should be lower than K!
Perplexity should be lower than K!
Perplexity should be lower than K!
Perplexity should be lower than K!
Error: Process completed with exit code 1.