Update convert.py

[adelavega]

Minor bug in conversion code

[codecov-io]

Codecov Report

Merging #637 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #637   +/-   ##
=======================================
  Coverage   82.22%   82.22%           
=======================================
  Files          57       57           
  Lines        2183     2183           
=======================================
  Hits         1795     1795           
  Misses        388      388

Impacted Files	Coverage Δ
neuroscout/populate/convert.py	86.13% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ced7403...aafc1fa. Read the comment docs.