fix: error message for empty object

[alexander-akait]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

better error for empty object

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #44 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #44   +/-   ##
=======================================
  Coverage   99.06%   99.06%           
=======================================
  Files           4        4           
  Lines         430      430           
  Branches      205      205           
=======================================
  Hits          426      426           
  Misses          4        4

Impacted Files	Coverage Δ
src/ValidationError.js	98.9% <100%> (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 692b437...519aa70. Read the comment docs.