MudPopover: Remove shadow if the popover is empty

[danielchalmers]

Description

Simply removes the shadow if the popover has no content. Resolves #10628

How Has This Been Tested?

visually

Type of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (fix or improvement to the website or code docs)

Before:

Video3.mp4

After:

Video2.mp4

Checklist

• The PR is submitted to the correct branch (dev).
• My code follows the code style of this project.
• I've added relevant tests.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.05%. Comparing base (e5f6908) to head (4147590).
Report is 8 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #11040      +/-   ##
==========================================
+ Coverage   91.01%   91.05%   +0.03%     
==========================================
  Files         429      429              
  Lines       13946    13956      +10     
  Branches     2696     2698       +2     
==========================================
+ Hits        12693    12707      +14     
+ Misses        648      646       -2     
+ Partials      605      603       -2     

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[Garderoben]

Nice!