Make modNamespace's translatePath method null-safe

[smg6511]

What does it do?

Replaces NULL $path with empty string.

Why is it needed?

The str_replace fn no longer quietly allows a null value to be passed to its subject param. Deprecation notices show in php logs when null is passed in php 8.1+.

How to test

1. Change a namespace's core or assets path to NULL via sql query.
2. Observe the php logs after clearing modx's cache (before loading this PR); you should see the deprecation notice(s).
3. Load the PR and clear cache again. There should be no deprecation notices (of the type seen in step 2).

Future Consideration

This could also be avoided by altering the path and assets_path columns in the namespaces table to be not null with default of empty string.

Related issue(s)/PR(s)

No related issue.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 21.55%. Comparing base (b1a02c3) to head (93c3847).
⚠️ Report is 50 commits behind head on 3.x.

Files with missing lines	Patch %	Lines
core/src/Revolution/modNamespace.php	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                3.x   #16763      +/-   ##
============================================
+ Coverage     21.53%   21.55%   +0.01%     
- Complexity    10734    10742       +8     
============================================
  Files           565      565              
  Lines         32540    32573      +33     
============================================
+ Hits           7007     7020      +13     
- Misses        25533    25553      +20     

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