Remove possible NPE when assumeTrue aborts a test

[daswass]

check list

• [✓] Read the contributing guide
• [✓] PR should be motivated, i.e. what does it fix, why, and if relevant how
• [✓] If possible / relevant include an example in the description, that could help all readers
  including project members to get a better picture of the change
• [✓] Avoid other runtime dependencies
• [✓] Meaningful commit history ; intention is important please rebase your commit history so that each
  commit is meaningful and help the people that will explore a change in 2 years
• [✓] The pull request follows coding style
• [✓] Mention Fixes #<issue number> in the description if relevant
• [✓] At least one commit should mention Fixes #<issue number> if relevant

[TimvdLippe]

Please add a regression test for this.

[codecov-io]

Codecov Report

Merging #1725 into release/2.x will decrease coverage by 0.02%.
The diff coverage is 60%.

@@                Coverage Diff                @@
##             release/2.x    #1725      +/-   ##
=================================================
- Coverage          86.53%   86.51%   -0.03%     
  Complexity          2481     2481              
=================================================
  Files                309      309              
  Lines               6528     6531       +3     
  Branches             818      819       +1     
=================================================
+ Hits                5649     5650       +1     
- Misses               681      682       +1     
- Partials             198      199       +1

Impacted Files	Coverage Δ	Complexity Δ
...va/org/mockito/junit/jupiter/MockitoExtension.java	86.95% <60%> (-3.75%)	13 <1> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1e3f69d...b36c9d5. Read the comment docs.

[TimvdLippe]

Closing per my review. Please reopen when a regression test is added.