Razor Service crashing

Issue Type: Bug

Opening a Blazor WASM application causes the Razor service to crash and shut down.

crash log:
```
--------------------------------------------------------------------------------
Razor.VSCode version 6.0.0-alpha.1.20521.3
--------------------------------------------------------------------------------
Razor's trace level is currently set to 'Off'
- To change Razor's trace level set 'razor.trace' to 'Off', 'Messages' or 'Verbose' and then restart VSCode.
- To report issues invoke the 'Report a Razor issue' command via the command palette.
-----------------------------------------------------------------------------------------------------------------------------

Unhandled exception. OmniSharp.Extensions.JsonRpc.Server.MethodNotSupportedException: Method not found: 'razor/serverReady'.
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.Returning[TResponse](CancellationToken cancellationToken)
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.ReturningVoid(CancellationToken cancellationToken)
at Microsoft.AspNetCore.Razor.LanguageServer.RazorServerReadyPublisher.ProjectSnapshotManager_Changed(Object sender, ProjectChangeEventArgs args) in /_/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorServerReadyPublisher.cs:line 63
at System.Threading.Tasks.Task.<>c.b__140_1(Object state)
at System.Threading.QueueUserWorkItemCallbackDefaultContext.Execute()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
[Info - 8:04:35 AM] Connection to server got closed. Server will restart.
Unhandled exception. OmniSharp.Extensions.JsonRpc.Server.MethodNotSupportedException: Method not found: 'razor/serverReady'.
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.Returning[TResponse](CancellationToken cancellationToken)
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.ReturningVoid(CancellationToken cancellationToken)
at Microsoft.AspNetCore.Razor.LanguageServer.RazorServerReadyPublisher.ProjectSnapshotManager_Changed(Object sender, ProjectChangeEventArgs args) in /_/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorServerReadyPublisher.cs:line 63
at System.Threading.Tasks.Task.<>c.b__140_1(Object state)
at System.Threading.QueueUserWorkItemCallbackDefaultContext.Execute()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
[Info - 8:04:37 AM] Connection to server got closed. Server will restart.
Unhandled exception. OmniSharp.Extensions.JsonRpc.Server.MethodNotSupportedException: Method not found: 'razor/serverReady'.
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.Returning[TResponse](CancellationToken cancellationToken)
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.ReturningVoid(CancellationToken cancellationToken)
at Microsoft.AspNetCore.Razor.LanguageServer.RazorServerReadyPublisher.ProjectSnapshotManager_Changed(Object sender, ProjectChangeEventArgs args) in /_/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorServerReadyPublisher.cs:line 63
at System.Threading.Tasks.Task.<>c.b__140_1(Object state)
at System.Threading.QueueUserWorkItemCallbackDefaultContext.Execute()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
[Info - 8:04:39 AM] Connection to server got closed. Server will restart.
Unhandled exception. OmniSharp.Extensions.JsonRpc.Server.MethodNotSupportedException: Method not found: 'razor/serverReady'.
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.Returning[TResponse](CancellationToken cancellationToken)
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.ReturningVoid(CancellationToken cancellationToken)
at Microsoft.AspNetCore.Razor.LanguageServer.RazorServerReadyPublisher.ProjectSnapshotManager_Changed(Object sender, ProjectChangeEventArgs args) in /_/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorServerReadyPublisher.cs:line 63
at System.Threading.Tasks.Task.<>c.b__140_1(Object state)
at System.Threading.QueueUserWorkItemCallbackDefaultContext.Execute()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
[Info - 8:04:41 AM] Connection to server got closed. Server will restart.
Unhandled exception. OmniSharp.Extensions.JsonRpc.Server.MethodNotSupportedException: Method not found: 'razor/serverReady'.
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.Returning[TResponse](CancellationToken cancellationToken)
at OmniSharp.Extensions.JsonRpc.ResponseRouter.ResponseRouterReturnsImpl.ReturningVoid(CancellationToken cancellationToken)
at Microsoft.AspNetCore.Razor.LanguageServer.RazorServerReadyPublisher.ProjectSnapshotManager_Changed(Object sender, ProjectChangeEventArgs args) in /_/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorServerReadyPublisher.cs:line 63
at System.Threading.Tasks.Task.<>c.b__140_1(Object state)
at System.Threading.QueueUserWorkItemCallbackDefaultContext.Execute()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
[Error - 8:04:43 AM] Connection to server got closed. Server will not be restarted.
[Client - 8:04:43 AM] (Error) Failed when activating Razor VSCode.
undefined
Stack Trace:
undefined

```

Extension version: 1.23.5
VS Code version: Code - Exploration 1.51.0-exploration (f5e2e8ba8af696d6a933903e28698d36831d3204, 2020-10-27T06:50:53.302Z)
OS version: Darwin x64 19.6.0

System Info

|Item|Value|
|---|---|
|CPUs|Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz (12 x 2600)|
|GPU Status|2d_canvas: enabled
gpu_compositing: enabled
metal: disabled_off
multiple_raster_threads: enabled_on
oop_rasterization: enabled
opengl: enabled_on
protected_video_decode: unavailable_off
rasterization: enabled
skia_renderer: disabled_off_ok
video_decode: enabled
webgl: enabled
webgl2: enabled|
|Load (avg)|3, 3, 2|
|Memory (System)|32.00GB (8.23GB free)|
|Process Argv|-psn_0_6415902|
|Screen Reader|no|
|VM|18%|