UnitsNetBaseJsonConverter minor bug fix for compatibility with UnitsNet 6.0.0-pre017

[andrewmeservy]

• Simple bug fix to make UnitsNet.Serialization.JsonNet compatible with the newest prerelease version of UnitsNet (6.0.0-pre017)

The fix simply replaces a null forgiving operator with an actual null-check and return. It will throw an exception if it fails the null check.

[andrewmeservy]

not sure why build checks fail - I didn't change that much and they seem like permissions errors rather than something with the code? lmk if there is something I need to do on my end!

[angularsen]

Thanks, what use case does this fix exactly?

I'm going to hold off on merging this until after #1544 , since it already touches hard onto serialization and I want to avoid merge conflicts towards it.

It can take some time to get that merged though, I have had little time to spare on this project lately, but maybe in the upcoming holidays.

[angularsen]

not sure why build checks fail - I didn't change that much and they seem like permissions errors rather than something with the code? lmk if there is something I need to do on my end!

No idea, seems like a hiccup in the build. Other PR builds are fine. I'll requeue this one.

https://dev.azure.com/unitsnet/Units.NET/_build/results?buildId=1410&view=logs&j=3dc8fd7e-4368-5a92-293e-d53cefc8c4b3&t=7bf8b4d7-347c-5dd5-5473-a01d1b8b437c

Starting: Install .NET nanoFramework MSBuild components
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Task         : Install .NET nanoFramework MSBuild components
Description  : Install .NET nanoFramework MSBuild components allowing building a .NET nanoFramework C# application with msbuild.
Version      : 1.256.0
Author       : .NET nanoFramework Project Contributors
Help         : 
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VS is: Visual Studio Enterprise 2022
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Finishing: Install .NET nanoFramework MSBuild components