Fix NPE while adding "response_body_size" breadcrumb (#1907)

[neseleznev]

📜 Description

Closes #1907 , see description there

💚 How did you test it?

Tested by researching API of dependency (OpenFeign)

📝 Checklist

• I reviewed the submitted code
• I didn't add tests, because it requires significant refactoring so that length could be null Integer
• I updated the docs if needed
• No breaking changes

[codecov-commenter]

Codecov Report

Merging #1908 (b4e0206) into main (33bdce3) will decrease coverage by 0.00%.
The diff coverage is 50.00%.

@@             Coverage Diff              @@
##               main    #1908      +/-   ##
============================================
- Coverage     75.42%   75.42%   -0.01%     
  Complexity     2244     2244              
============================================
  Files           225      225              
  Lines          8026     8025       -1     
  Branches        852      851       -1     
============================================
- Hits           6054     6053       -1     
  Misses         1562     1562              
  Partials        410      410              

Impacted Files	Coverage Δ
...in/java/io/sentry/openfeign/SentryFeignClient.java	96.15% <50.00%> (-0.08%)	⬇️

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[maciejwalkowiak]

Thanks for fix!

[romtsn]

Thanks @neseleznev for fixing this!