Update check for nothing in ChebyshevT

[jishnub]

Use === instead of == in the check for nothing

[codecov]

Codecov Report

Merging #422 (a6a98bd) into master (8116678) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #422   +/-   ##
=======================================
  Coverage   83.70%   83.70%           
=======================================
  Files          23       23           
  Lines        2798     2798           
=======================================
  Hits         2342     2342           
  Misses        456      456           

Impacted Files	Coverage Δ
src/polynomials/ChebyshevT.jl	94.05% <100.00%> (ø)

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[jverzani]

Thanks!

That failed test is due to some randomness in the algorithm being tested. It should be much more robust. It failed 2 times today, and never in the past. I'll open an issue, but it won't hold this back.