foverlaps: better error message when intervals have NA

[arunsrinivasan]

Closes #3007.

[codecov]

Codecov Report

Merging #3418 into master will decrease coverage by 0.1%.
The diff coverage is 92.77%.

@@            Coverage Diff             @@
##           master    #3418      +/-   ##
==========================================
- Coverage   95.12%   95.02%   -0.11%     
==========================================
  Files          65       65              
  Lines       12127    12249     +122     
==========================================
+ Hits        11536    11639     +103     
- Misses        591      610      +19

Impacted Files	Coverage Δ
R/foverlaps.R	97.98% <76.92%> (-2.02%)	⬇️
src/ijoin.c	94.66% <95.71%> (-2.79%)	⬇️

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[codecov]

Codecov Report

Merging #3418 into master will decrease coverage by 0.1%.
The diff coverage is 92.77%.

@@            Coverage Diff             @@
##           master    #3418      +/-   ##
==========================================
- Coverage   95.12%   95.02%   -0.11%     
==========================================
  Files          65       65              
  Lines       12127    12249     +122     
==========================================
+ Hits        11536    11639     +103     
- Misses        591      610      +19

Impacted Files	Coverage Δ
R/foverlaps.R	97.98% <76.92%> (-2.02%)	⬇️
src/ijoin.c	94.66% <95.71%> (-2.79%)	⬇️

---

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 8c43750...0691e9c. Read the comment docs.