fix: potential NPE of WriteParameters#hashCode

[bednar]

Closes #482

Proposed Changes

Fixed potential NPE for WriteParameters#hashCode.

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• mvn test completes successfully
• Commit messages are conventional
• Sign CLA (if not already signed)

[vlastahajek]

LGTM

[codecov-commenter]

Codecov Report

Base: 88.38% // Head: 88.42% // Increases project coverage by +0.04% 🎉

Coverage data is based on head (36ae228) compared to base (9b07e6e).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@ Coverage Diff @@ ## master #483 +/- ## ============================================ + Coverage 88.38% 88.42% +0.04%  - Complexity 764 777 +13  ============================================ Files 172 172 Lines 7008 7008 Branches 378 380 +2 ============================================ + Hits 6194 6197 +3  + Misses 694 692 -2  + Partials 120 119 -1 

Impacted Files	Coverage Δ
...ava/com/influxdb/client/write/WriteParameters.java	83.92% <100.00%> (+3.57%)	⬆️
...a/com/influxdb/client/internal/BucketsApiImpl.java	71.16% <0.00%> (+0.61%)	⬆️

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