fix: do not crash with 'false' aliases

[alexander-akait]

This PR contains a:

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

Motivation / Use-Case

fixes #1291

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #1292 (dfabb21) into master (2388439) will increase coverage by 0.49%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1292      +/-   ##
==========================================
+ Coverage   97.72%   98.22%   +0.49%     
==========================================
  Files          11       11              
  Lines         835      844       +9     
  Branches      279      283       +4     
==========================================
+ Hits          816      829      +13     
+ Misses         16       12       -4     
  Partials        3        3              

Impacted Files	Coverage Δ
src/plugins/postcss-icss-parser.js	100.00% <100.00%> (ø)
src/plugins/postcss-import-parser.js	100.00% <100.00%> (ø)
src/plugins/postcss-url-parser.js	97.63% <100.00%> (+0.02%)	⬆️
src/utils.js	97.15% <0.00%> (+1.03%)	⬆️

---

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 2388439...dfabb21. Read the comment docs.