Move null guard statement up in NuGetComponentDetector.IsValidPath to avoid uncessary throw of ArgumentNullException in FileInfo constructor

[WesHaze]

Moves guard statement up in the NuGetComponentDetector to avoid unnecessary throw in the FileInfo constructor

[pauld-msft]

Thanks for submitting this!

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 89.6%. Comparing base (a72b623) to head (56b27f4).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...etection.Detectors/nuget/NuGetComponentDetector.cs	0.0%	3 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1371   +/-   ##
=====================================
  Coverage   89.6%   89.6%           
=====================================
  Files        402     402           
  Lines      31734   31734           
  Branches    1959    1959           
=====================================
  Hits       28465   28465           
  Misses      2852    2852           
  Partials     417     417           

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[github-actions]

👋 Hi! It looks like you modified some files in the Detectors folder.
You may need to bump the detector versions if any of the following scenarios apply:

• The detector detects more or fewer components than before
• The detector generates different parent/child graph relationships than before
• The detector generates different devDependencies values than before

If none of the above scenarios apply, feel free to ignore this comment 🙂