fix: Remove spaces around partition columns

[linliu-code]

Describe the issue this Pull Request addresses

Partition columns can be around by spaces during configuration, like \sC1, C1\s, or C1,\sC2. In those cases, NPE could be thrown since we cannot find any partition columns when spaces.

Summary and Changelog

Remove spaces around partition columns during parsing.

Impact

Avoid NPE.

Risk Level

None.

Documentation Update

Contributor's checklist

• Read through contributor's guide
• Enough context is provided in the sections above
• Adequate tests were added if applicable

[hudi-bot]

CI report:

• 278e556 Azure: SUCCESS

Bot commands

@hudi-bot supports the following commands:

• @hudi-bot run azure re-run the last Azure build

[voonhous]

Can we add tests for these?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.25%. Comparing base (1ff0506) to head (278e556).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18423      +/-   ##
============================================
- Coverage     68.26%   68.25%   -0.01%     
+ Complexity    27761    27754       -7     
============================================
  Files          2439     2439              
  Lines        134355   134356       +1     
  Branches      16210    16210              
============================================
- Hits          91715    91710       -5     
+ Misses        35543    35542       -1     
- Partials       7097     7104       +7     

Flag	Coverage Δ
common-and-other-modules	44.36% <100.00%> (+<0.01%)	⬆️
hadoop-mr-java-client	44.97% <100.00%> (-0.02%)	⬇️
spark-client-hadoop-common	48.40% <100.00%> (+<0.01%)	⬆️
spark-java-tests	48.78% <100.00%> (+<0.01%)	⬆️
spark-scala-tests	45.29% <100.00%> (-0.01%)	⬇️
utilities	38.37% <100.00%> (-0.01%)	⬇️

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

Files with missing lines	Coverage Δ
...rg/apache/hudi/common/table/HoodieTableConfig.java	94.83% <100.00%> (+<0.01%)	⬆️

... and 15 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[yihua]

🤖 This review was generated by an AI agent and may contain mistakes. Please verify any suggestions before applying.

LGTM — the fix is simple and correct. Trimming before the empty-string filter is the right order, and the trimmed field names flow cleanly into getPartitionFieldWithoutKeyGenPartitionType. One thing worth noting: a reviewer has already asked for a dedicated test covering the leading/trailing-space scenario (e.g. " C1", "C1 ", "C1, C2"), and the contributor's checklist item for tests is still unchecked — it'd be good to add one before merging.