fix: Filter with date and document with nil date value

[fredcarle]

Relevant issue(s)

Resolves #2945

Description

This PR ensure that no error occurs when filtering for a date while having documents with nil date value.

Tasks

• I made sure the code is well commented, particularly hard-to-understand areas.
• I made sure the repository-held documentation is changed accordingly.
• I made sure the pull request title adheres to the conventional commit style (the subset used in the project can be found in tools/configs/chglog/config.yml).
• I made sure to discuss its limitations such as threats to validity, vulnerability to mistake and misuse, robustness to invalidation of assumptions, resource requirements, ...

How has this been tested?

added filter integration tests for date

Specify the platform(s) on which this was tested:

• MacOS

[islamaliev]

LGTM!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.28%. Comparing base (53e55c4) to head (761ce7b).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #2946   +/-   ##
========================================
  Coverage    79.28%   79.28%           
========================================
  Files          326      326           
  Lines        24862    24870    +8     
========================================
+ Hits         19711    19718    +7     
+ Misses        3737     3735    -2     
- Partials      1414     1417    +3     

Flag	Coverage Δ
all-tests	79.28% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
internal/connor/ge.go	60.00% <100.00%> (+2.42%)	⬆️
internal/connor/gt.go	60.00% <100.00%> (+2.42%)	⬆️
internal/connor/le.go	57.14% <100.00%> (+2.60%)	⬆️
internal/connor/lt.go	60.00% <100.00%> (+2.42%)	⬆️

... and 13 files with indirect coverage changes

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