fix: json marshal l errors when parsing poll response from klaviyo

[koladilip]

Description

There is a bug in the Klaviyo implementation where, at times, we receive an empty import ID from the upload. However, when we poll with an empty import ID, we encounter parsing errors because Klaviyo returns a list response when the import ID is empty.

Linear Ticket

https://linear.app/rudderstack/issue/INT-2820/klaviyo-bulk-upload-at-times-they-are-running-into-errors
Resolves INT-2820

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[codecov]

Codecov Report

Attention: Patch coverage is 42.85714% with 8 lines in your changes missing coverage. Please review.

Project coverage is 73.47%. Comparing base (e4cb7f1) to head (b9504e3).

Files with missing lines	Patch %	Lines
...destinationmanager/klaviyobulkupload/apiService.go	12.50%	7 Missing ⚠️
...tionmanager/klaviyobulkupload/klaviyobulkupload.go	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##           release/1.38.x    #5316      +/-   ##
==================================================
+ Coverage           73.43%   73.47%   +0.03%     
==================================================
  Files                 425      425              
  Lines               59973    59981       +8     
==================================================
+ Hits                44044    44072      +28     
+ Misses              13450    13440      -10     
+ Partials             2479     2469      -10     

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[krishna2020]

does this mean all the events that were part of unsuccessful upload gets re-tried in next attempt as they don't get marked as queued ?