Null pointer exception when reading a complex type with empty arrays.…

[mregen]

… (#2798)

The server under test has a extension object with a complex type. Type id = {nsu=http://opcfoundation.org/UA/Machinery/Result/;i=5008}. This contains something with a variant array that is null though (-1). SetProperty should support setting a Array that is null. Therefore, test for null collection (case when length was encoded as -1) before dereferencing ahead of the ToArrray() conversion to Array.

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 25 lines in your changes missing coverage. Please review.

Project coverage is 57.23%. Comparing base (cb621df) to head (3672ebe).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
Stack/Opc.Ua.Core/Types/Encoders/BinaryDecoder.cs	0.00%	0 Missing and 25 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2804      +/-   ##
==========================================
+ Coverage   55.31%   57.23%   +1.91%     
==========================================
  Files         349      352       +3     
  Lines       66056    75520    +9464     
  Branches    13549    15988    +2439     
==========================================
+ Hits        36541    43223    +6682     
- Misses      25631    27870    +2239     
- Partials     3884     4427     +543     

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