remove incorrect assert (fixes #1561)

[mlubin]

No description provided.

[codecov]

Codecov Report

Merging #1565 into master will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1565      +/-   ##
==========================================
+ Coverage   89.49%   89.54%   +0.05%     
==========================================
  Files          27       27              
  Lines        3626     3625       -1     
==========================================
+ Hits         3245     3246       +1     
+ Misses        381      379       -2

Impacted Files	Coverage Δ
src/nlp.jl	90.82% <ø> (+0.33%)	⬆️

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