RUM-1520 prevent false positive warning

[xgouchet]

What does this PR do?

Prevent a false positive warning in the logcat when the logs feature is available but no fields is provided to the span.log() method

[codecov-commenter]

Codecov Report

Merging #1815 (a32ff40) into develop (88069eb) will decrease coverage by 0.07%.
The diff coverage is 0.00%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1815      +/-   ##
===========================================
- Coverage    83.52%   83.45%   -0.07%     
===========================================
  Files          466      466              
  Lines        16368    16364       -4     
  Branches      2455     2452       -3     
===========================================
- Hits         13670    13656      -14     
- Misses        2028     2036       +8     
- Partials       670      672       +2     

Files	Coverage Δ
.../trace/internal/handlers/AndroidSpanLogsHandler.kt	87.76% <0.00%> (-1.83%)	⬇️

... and 19 files with indirect coverage changes