Check whether property value has changed after transform

[philippjfr]

Fixes #7430

[codecov]

Codecov Report

Attention: Patch coverage is 94.44444% with 2 lines in your changes missing coverage. Please review.

Project coverage is 82.09%. Comparing base (7f850dc) to head (da1c909).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
panel/reactive.py	91.30%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7432      +/-   ##
==========================================
+ Coverage   82.07%   82.09%   +0.01%     
==========================================
  Files         337      337              
  Lines       50644    50676      +32     
==========================================
+ Hits        41565    41601      +36     
+ Misses       9079     9075       -4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.