feat: make json-ld expansion fails if titanium returns empty result

[ndr-brt]

What this PR changes/adds

Make TitaniumJsonLd expansion fails if the result is empty (that usually happens when there are no expanded properties, e.g. when there are no namespaced properties withouth the @context property set).

It also fix a nit that avoided the validator to work correctly on the update method

Why it does that

improve error messages

Further notes

Linked Issue(s)

Closes #3172

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[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.07 🎉

Comparison is base (abf2443) 65.35% compared to head (7afecbe) 65.43%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3192      +/-   ##
==========================================
+ Coverage   65.35%   65.43%   +0.07%     
==========================================
  Files         835      835              
  Lines       16794    16800       +6     
  Branches      925      925              
==========================================
+ Hits        10976    10993      +17     
+ Misses       5449     5439      -10     
+ Partials      369      368       -1     

Impacted Files	Coverage Δ
...in/java/org/eclipse/edc/jsonld/TitaniumJsonLd.java	93.10% <100.00%> (ø)
...nector/api/management/asset/AssetApiExtension.java	90.90% <100.00%> (+90.90%)	⬆️
...ement/asset/validation/AssetEntryDtoValidator.java	86.95% <100.00%> (+3.62%)	⬆️

... and 3 files with indirect coverage changes

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