Fix concatenation with zero n_coeffs

[thangleiter]

Instead of populating a zeros array, populate a nan array and check for those.

[codecov]

Codecov Report

Merging #59 (64d01da) into master (dc1ccd2) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #59   +/-   ##
=======================================
  Coverage   97.27%   97.27%           
=======================================
  Files           9        9           
  Lines        2203     2203           
  Branches      499      498    -1     
=======================================
  Hits         2143     2143           
  Misses         26       26           
  Partials       34       34           

Impacted Files	Coverage Δ
filter_functions/pulse_sequence.py	97.32% <100.00%> (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 dc1ccd2...64d01da. Read the comment docs.