fix(ui2): check organization is not None

[natemoo-re]

Follow-up to #101654, switching the feature check to only happen if organization is not None.

🤞 should fix https://sentry.sentry.io/issues/7027783052/

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/sentry/web/frontend/react_page.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #103372      +/-   ##
===========================================
+ Coverage   80.34%    80.67%   +0.33%     
===========================================
  Files        9237      9237              
  Lines      394545    394545              
  Branches    25146     25146              
===========================================
+ Hits       316986    318298    +1312     
+ Misses      77112     75800    -1312     
  Partials      447       447