Fix pagination visibility handling on media library overview page

[Aaditya0411]

Description

Fixes an issue where the pagination container visibility was accessed
without checking if the element exists on the media library overview page.

Changes

• Added a null-check before modifying pagination container visibility
• Prevents potential JavaScript runtime errors and UI inconsistencies

Fixes #6154

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.94%. Comparing base (8a585eb) to head (39db9f0).
⚠️ Report is 42 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #6156   +/-   ##
==========================================
  Coverage      51.94%   51.94%           
  Complexity      7964     7964           
==========================================
  Files            733      733           
  Lines          25569    25569           
==========================================
  Hits           13282    13282           
  Misses         12287    12287           

Flag	Coverage Δ
behat	49.70% <ø> (ø)
phpunit	10.38% <ø> (ø)

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[Aaditya0411]

Hi Maintainers

It looks like the failing Behat test (api-projects search) might be unrelated to this frontend pagination change.
Could you please confirm whether this failure is expected, or if I should rebase the branch with the latest develop?

I’m happy to update the PR as needed. Thanks for your time and review!