Fix NPE when reading ZK address from controller config

[Jackie-Jiang]

Fix the NPE in #9745

[61yao]

Nit: are we able to cover this in unit test if possible?

[Jackie-Jiang]

Nit: are we able to cover this in unit test if possible?

The change in this PR basically change the NPE to a more readable error message, and IMO it is a little bit overkilling to add a test for it

[codecov-commenter]

Codecov Report

Merging #9751 (58aaaba) into master (3724ba2) will increase coverage by 35.65%.
The diff coverage is 66.66%.

@@              Coverage Diff              @@
##             master    #9751       +/-   ##
=============================================
+ Coverage     34.69%   70.35%   +35.65%     
- Complexity      190     5001     +4811     
=============================================
  Files          1965     1965               
  Lines        105115   105108        -7     
  Branches      15909    15908        -1     
=============================================
+ Hits          36474    73950    +37476     
+ Misses        65542    26017    -39525     
- Partials       3099     5141     +2042     

Flag	Coverage Δ
integration1	25.24% <66.66%> (+0.11%)	⬆️
integration2	24.49% <66.66%> (?)
unittests1	67.96% <ø> (?)
unittests2	15.83% <66.66%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...va/org/apache/pinot/controller/ControllerConf.java	59.68% <66.66%> (+2.70%)	⬆️
.../helix/core/realtime/SegmentCompletionManager.java	72.15% <0.00%> (-0.82%)	⬇️
...pache/pinot/core/query/utils/idset/EmptyIdSet.java	25.00% <0.00%> (ø)
...inot/core/util/SegmentCompletionProtocolUtils.java	57.69% <0.00%> (ø)
...anager/realtime/SegmentBuildTimeLeaseExtender.java	63.23% <0.00%> (ø)
.../core/realtime/PinotLLCRealtimeSegmentManager.java	72.07% <0.00%> (+0.45%)	⬆️
...che/pinot/broker/routing/BrokerRoutingManager.java	86.07% <0.00%> (+0.55%)	⬆️
...e/pinot/common/function/TransformFunctionType.java	100.00% <0.00%> (+0.94%)	⬆️
...x/core/realtime/MissingConsumingSegmentFinder.java	87.09% <0.00%> (+1.07%)	⬆️
.../apache/pinot/common/exception/QueryException.java	94.44% <0.00%> (+1.11%)	⬆️
... and 1118 more

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