[SERVICES-1832] fix logs processor lastProcessedTimestamp

[claudiulataretu]

Reasoning

• wrong check for cached value

Proposed Changes

• check for undefined for values cached

How to test

• N/A

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (02882e6) 56.15% compared to head (94d20d5) 56.15%.
Report is 1 commits behind head on feat/nestjs-sdk-integration.

Additional details and impacted files

@@                     Coverage Diff                      @@
##           feat/nestjs-sdk-integration    #1188   +/-   ##
============================================================
  Coverage                        56.15%   56.15%           
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  Files                              235      235           
  Lines                             7818     7818           
  Branches                           519      519           
============================================================
  Hits                              4390     4390           
  Misses                            2986     2986           
  Partials                           442      442           

Flag	Coverage Δ
unittests	56.15% <ø> (ø)

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