fix: prevent NPE in RemoteStorageHelper.cleanBuckets

[Gerschtli]

The method getEventBasedHold and getTemporaryHold return Boolean objects which are either true, false or null. In case of a null value, this produced a NPE.

[codecov]

Codecov Report

Merging #492 into master will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master     #492      +/-   ##
============================================
- Coverage     64.60%   64.59%   -0.02%     
+ Complexity      626      617       -9     
============================================
  Files            32       32              
  Lines          5235     5236       +1     
  Branches        506      508       +2     
============================================
  Hits           3382     3382              
- Misses         1694     1695       +1     
  Partials        159      159              

Impacted Files	Coverage Δ	Complexity Δ
...gle/cloud/storage/testing/RemoteStorageHelper.java	64.00% <0.00%> (-0.52%)	9.00 <0.00> (ø)

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