Fix the NPE from IS update metrics

[Jackie-Jiang]

Fix the NPE introduced in #13266
When updateIdealState() is invoked from broker, it can throw NPE because ControllerMetrics is not registered.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 61.99%. Comparing base (59551e4) to head (2ec9f75).
Report is 551 commits behind head on master.

Files	Patch %	Lines
...g/apache/pinot/common/utils/helix/HelixHelper.java	0.00%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #13313      +/-   ##
============================================
+ Coverage     61.75%   61.99%   +0.24%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2538     +102     
  Lines        133233   139499    +6266     
  Branches      20636    21593     +957     
============================================
+ Hits          82274    86482    +4208     
- Misses        44911    46518    +1607     
- Partials       6048     6499     +451     

Flag	Coverage Δ
custom-integration1	?
integration	<0.01% <0.00%> (-0.01%)	⬇️
integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration2	0.00% <0.00%> (ø)
java-11	61.99% <0.00%> (+0.28%)	⬆️
java-21	<0.01% <0.00%> (-61.63%)	⬇️
skip-bytebuffers-false	61.99% <0.00%> (+0.24%)	⬆️
skip-bytebuffers-true	<0.01% <0.00%> (-27.73%)	⬇️
temurin	61.99% <0.00%> (+0.24%)	⬆️
unittests	61.99% <0.00%> (+0.24%)	⬆️
unittests1	46.51% <0.00%> (-0.39%)	⬇️
unittests2	27.76% <0.00%> (+0.03%)	⬆️

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[gortiz]

I've created a NOOP registry in #13032, so this kind of issues shouldn't be problematic in the future.