Lists of Enums that are assigned values through the editor have incorrect values at runtime

[491625]

Godot version

3.3.3

System information

Windows 10

Issue description

I have a list of enum values that is exposed through the editor via the [Export] attribute. At runtime, the first entry in that list has an incorrect value that doesn't correspond to any member of the enum.

I've repro'd the problem in a stripped down project that only contains the following script assigned to a single Node2D.

using Godot;
using System;
using System.Collections.Generic;

public class NodeWithEnumList : Node2D
{
	
	[Export]
	public List<TestEnum> EnumVals {get; set;}
	
	// Called when the node enters the scene tree for the first time.
	public override void _Ready()
	{
		foreach(var enumVal in EnumVals)
		{
			Console.WriteLine($"You have an enumVal of {enumVal}");
		}
	}

	public enum TestEnum
	{
		firstVal,
		secondVal
	}

}

Here's what's configured for that Node2D in the editor.

And here's what gets printed out in the console.

Steps to reproduce

Repro steps are included in the 'Issue Description' above, but here's a quick summary of how to repro with the project attached.

1. Start up the project and make sure that the 'Enum Vals' property on the Node2D has at least 1 entry assigned to it.
2. Play the project (you may want to have a debugger attached and a breakpoint in the _Ready() function in NodeWithEnumList.cs)
3. Look at the console output, or use the debugger to inspect the value of the EnumVals variable.

Minimal reproduction project

EnumBugTest.zip

[Calinou]

Duplicate of #42926.