Reuse of existing file

### Godot version

4.7.1 stable

### Godot .NET packages version

version 8.0

### System information

Fedora 44 KDE Plasma, Ryzen 5 1400 16GB RAM

### .NET information

.NET SDK: Version: 8.0.128 Commit: d091372eb2 Workload version: 8.0.100-manifests.f89b5038 Runtime Environment: OS Name: fedora OS Version: 44 OS Platform: Linux RID: fedora.44-x64 Base Path: /usr/lib64/dotnet/sdk/8.0.128/ .NET workloads installed: Workload version: 8.0.100-manifests.f89b5038 There are no installed workloads to display. Host: Version: 8.0.28 Architecture: x64 Commit: 46295af582 .NET SDKs installed: 8.0.128 [/usr/lib64/dotnet/sdk] .NET runtimes installed: Microsoft.AspNetCore.App 8.0.28 [/usr/lib64/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.NETCore.App 8.0.28 [/usr/lib64/dotnet/shared/Microsoft.NETCore.App] Other architectures found: None Environment variables: Not set global.json file: Not found Learn more: https://aka.ms/dotnet/info Download .NET: https://aka.ms/dotnet/download

### Issue description

when adding a script to autoload, it both accepts and refuses the use of an existing file

### Steps to reproduce

prject settings > Globals Tab > Add Script > choose and existing script

### Minimal reproduction project

Isnt project specific

Reproduce the behavior in Project Settings > Globals > Add Script by choosing an existing script, using the reported Godot 4.7.1 .NET environment as a reference. Compare the states where the editor accepts and refuses the file; done means the existing-file choice has one consistent, correct outcome.

Written by the indexing model from the issue text.