re #52: fixes fail on json preprocessing

[biojppm]

Fixes #52

[coveralls]

Pull Request Test Coverage Report for Build 463

• 26 of 26 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 92.776%

---

Totals
Change from base Build 459:	0.04%
Covered Lines:	3429
Relevant Lines:	3696

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 463

• 26 of 26 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 92.776%

---

Totals
Change from base Build 459:	0.04%
Covered Lines:	3429
Relevant Lines:	3696

---

💛 - Coveralls

[codecov]

Codecov Report

Merging #62 into master will increase coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #62      +/-   ##
==========================================
+ Coverage   93.28%   93.36%   +0.07%     
==========================================
  Files          58       58              
  Lines        5676     5729      +53     
==========================================
+ Hits         5295     5349      +54     
+ Misses        381      380       -1     

Impacted Files	Coverage Δ
src/c4/yml/preprocess.cpp	95.95% <100.00%> (+1.33%)	⬆️
test/preprocess.cpp	97.29% <100.00%> (+4.70%)	⬆️

---

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 829f724...b22d12f. Read the comment docs.