Fix #7380: Preview Panel with notifications enabled

[MP-MaximilianLattka]

• Fixes regression bug: https://github.com/holoviz/panel/issues/7380
• Reverts change from 15a8241a00ac35e883bc4aa4563d9a82b642b6f8
• os.fspath does not accept None

[codecov[bot]]

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 :warning:

Additional details and impacted files

```diff @@ 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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