Fixed the potential NPE of schema quota

[Caideyipi]

Description

As the title said.

---

This PR has:

• been self-reviewed.
  • concurrent read
  • concurrent write
  • concurrent read and write
• added documentation for new or modified features or behaviors.
• added Javadocs for most classes and all non-trivial methods.
• added or updated version, license, or notice information
• added comments explaining the "why" and the intent of the code wherever would not be obvious
  for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold
  for code coverage.
• added integration tests.
• been tested in a test IoTDB cluster.

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Key changed/added classes (or packages if there are too many classes) in this PR

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 39.48%. Comparing base (f445132) to head (77ae316).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
.../iotdb/confignode/manager/ClusterQuotaManager.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #17140      +/-   ##
============================================
- Coverage     39.49%   39.48%   -0.01%     
  Complexity      282      282              
============================================
  Files          5097     5097              
  Lines        341191   341190       -1     
  Branches      43457    43456       -1     
============================================
- Hits         134745   134728      -17     
- Misses       206446   206462      +16     

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