fix: fix error when children include invalid element

[AshoneA]

fix error when first-level children include invalid element

[vercel]

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[afc163]

should be return child?

[AshoneA]

If an element is invalid, I think there's no difference between child and null. return child should be also fine.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.98%. Comparing base (4b3d17c) to head (f91a763).
⚠️ Report is 3 commits behind head on 2.x.

Additional details and impacted files

@@           Coverage Diff           @@
##              2.x     #286   +/-   ##
=======================================
  Coverage   98.98%   98.98%           
=======================================
  Files           5        5           
  Lines         689      691    +2     
  Branches      209      210    +1     
=======================================
+ Hits          682      684    +2     
  Misses          7        7           

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