fix: Attempted to assign to readonly property

[ahmadfsalameh]

TypeError: Attempted to assign to readonly property.

Checklist

• only relevant code is changed (make a diff before you submit the PR)
• run tests npm run test
• tests are included
• commit message and code follows the Developer's Certification of Origin

Checklist (for documentation change)

• only relevant documentation part is changed (make a diff before you submit the PR)
• motivation/reason is provided
• commit message and code follows the Developer's Certification of Origin

[adrai]

Can you provide the original issue for this PR?
Or at least describe with more detail information what this PR exactly should fix?

[coveralls]

coverage: 97.082%. remained the same
when pulling b02ffef on ahmadfsalameh:master
into c9a73eb on i18next:master.