Ensure CompositeWidget can be populated in callback

[philippjfr]

Fixes #7052

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.73%. Comparing base (838fcc3) to head (09b5965).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7636   +/-   ##
=======================================
  Coverage   86.73%   86.73%           
=======================================
  Files         346      346           
  Lines       52051    52052    +1     
=======================================
+ Hits        45148    45149    +1     
  Misses       6903     6903           

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