Fix #7380: Preview Panel with notifications enabled

[MP-MaximilianLattka]

• Fixes regression bug: Preview with Panel broken with notifications turned on #7380
• Reverts change from 15a8241
• os.fspath does not accept None

[codecov]

Codecov Report

Attention: Patch coverage is 62.50000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 82.31%. Comparing base (6c322c5) to head (6c7b37e).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
panel/io/resources.py	62.50%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7466      +/-   ##
==========================================
+ Coverage   82.30%   82.31%   +0.01%     
==========================================
  Files         338      338              
  Lines       50838    50896      +58     
==========================================
+ Hits        41840    41893      +53     
- Misses       8998     9003       +5     

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