#254 Prevents a null exception when there is no version.

[alexquintero]

The issue or feature being addressed

GitHub Issue -- When using [ApiVersionNeutral] a null exception is thrown.

Details on the issue fix or feature implementation

Adds a simple check to verify that there is in fact a VersionRouteDataToken before attempting to access it from the dictionary.

Confirm the following

• I have ensured that I have merged the latest changes from the dev branch
• I have successfully run a local build
• I have included the github issue number in my commits
• I have included unit tests for the issue/feature
  I am unsure how to add this to your current test framework given that it requires use of Microsoft.AspNetCore.Mvc.Versioning which would subsequently require it in the TestController. Perhaps you could give me some guidance on where/how you'd like this to be done.

[alhardy]

Thanks @alexquintero