NullReferenceException from PSES if no folder is open when Preview Extension Loaded

[JustinGrote]

System Details

Using VSIX from #2304

System Details Output

11/18/2019 12:58:30 PM [ERROR] - Error: Internal Error - System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.PowerShell.EditorServices.Server.PsesLanguageServer.<>c.<<StartAsync>b__18_3>d.MoveNext() in D:\a\1\PowerShellEditorServices\src\PowerShellEditorServices\Server\PsesLanguageServer.cs:line 114
--- End of stack trace from previous location where exception was thrown ---
   at OmniSharp.Extensions.LanguageServer.Server.LanguageServer.MediatR.IRequestHandler<OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeParams,OmniSharp.Extensions.LanguageServer.Protocol.Models.InitializeResult>.Handle(InitializeParams request, CancellationToken token)
   at OmniSharp.Extensions.LanguageServer.Server.Pipelines.ResolveCommandPipeline`2.Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate`1 next)
   at MediatR.Pipeline.RequestPostProcessorBehavior`2.Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate`1 next)
   at MediatR.Pipeline.RequestPreProcessorBehavior`2.Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate`1 next)
   at OmniSharp.Extensions.JsonRpc.RequestRouterBase`1.RouteRequest(TDescriptor descriptor, Request request, CancellationToken token)

Expected Behaviour

Extension should load on a new window with no folder specified

Actual Behaviour

"Could not start language service"

Attached Logs

Follow the instructions in the troubleshooting docs
about capturing and sending logs.

[TylerLeonhardt]

Fix out for this - thanks for catching that!