Crash when clicking a resource property in the inspector while no scene is open

[Zylann]

Godot version

4.0 83d2673

System information

Windows 10 64 bits GLES3 GeForce GTX 1060 6GB/PCIe/SSE2

Issue description

I have a resource containing another. If I open it in the inspector and click the property, Godot crashes.

EditorPropertyResource::_resource_selected assumes there is an open scene, causing an access violation.

Steps to reproduce

1. Close all scenes
2. Create a GradientTexture
3. Assign gradient to a new Gradient in place
4. Save the GradientTexture as a .tres file
5. Double-click the .tres file in the file system to open it in the inspector
6. Click the gradient property: observe a crash

Minimal reproduction project

InspectorEditSubResourceCrash.zip

[timothyqiu]

From #59496, CC @KoBeWi

Maybe it should skip when the resource is a builtin subresource.