dotnet watch crashes upon adding static files

### Describe the bug
I am repeatedly seeing crashes in dotnet watch when my process adds any static file to its sub-directories that dotnet watch is listening for file change events.

### To Reproduce

Start dotnet watch on a project which writes text file to one of the sub-directories. The process will crash.

### Exceptions (if any)

dotnet watch ⏳ Waiting for a file to change before restarting dotnet...
dotnet watch 🔄 Restart requested.
dotnet watch ❌ System.ArgumentNullException: Value cannot be null. (Parameter 'key')
at System.Collections.Generic.Dictionary`2.FindValue(TKey key)
at System.Collections.Generic.Dictionary`2.TryGetValue(TKey key, TValue& value)
at Microsoft.DotNet.Watcher.Tools.StaticFileHandler.HandleFileChangesAsync(IReadOnlyList`1 files, CancellationToken cancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.HotReloadDotNetWatcher.WatchAsync(CancellationToken shutdownCancellationToken)
at Microsoft.DotNet.Watcher.Program.RunAsync()
dotnet watch ❌ An unexpected error occurred

### Further technical details
Microsoft Visual Studio Community 2022 (64-bit) - Preview
Version 17.13.0 Preview 1.0

PS > dotnet --info
.NET SDK:
Version: 9.0.100-rc.2.24474.11
Commit: 315e1305db
Workload version: 9.0.100-manifests.4872d5d5
MSBuild version: 17.12.0-preview-24473-03+fea15fbd1

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22631
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\9.0.100-rc.2.24474.11\

.NET workloads installed:
There are no installed workloads to display.
Configured to use loose manifests when installing new manifests.

Host:
Version: 9.0.0-rc.2.24473.5
Architecture: x64
Commit: 990ebf52fc

.NET SDKs installed:
8.0.404 [C:\Program Files\dotnet\sdk]
9.0.100-rc.2.24474.11 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.35 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.10 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.0-rc.2.24474.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.35 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.0-rc.2.24473.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.35 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.10 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.0-rc.2.24474.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set

global.json file:
Not found

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