Tool fails to run with System.InvalidOperationException:

I tried to run the tool on a dotnet/runtime library and hit the following error:
```
Specified Docs xml locations:
- c:\src\dotnet\dotnet-api-docs\xml
Included assemblies:
- System.IO.Pipelines
Included namespaces:
- System.IO
Unhandled exception. System.InvalidOperationException: Sequence contains no elements
at System.Linq.ThrowHelper.ThrowNoElementsException()
at System.Linq.Enumerable.First[TSource](IEnumerable`1 source)
at Libraries.ToTripleSlashPorter.LoadVSInstance() in C:\src\carlossanlop\DocsPortingTool\Libraries\ToTripleSlashPorter.cs:line 439
at Libraries.ToTripleSlashPorter.Start(Configuration config) in C:\src\carlossanlop\DocsPortingTool\Libraries\ToTripleSlashPorter.cs:line 112
at DocsPortingTool.DocsPortingTool.Main(String[] args) in C:\src\carlossanlop\DocsPortingTool\Program\DocsPortingTool.cs:line 22
```

@carlossanlop