Specific exported Dictionary has null as default value

### Tested versions

4.5 dev1

### System information

W10

### Issue description

```GDScript
@tool
extends Node

const UI_COLOR = Color("0f1f24cc")
const UI_COLOR_BG = Color("0f1f24ff")
const UI_COLOR_HEADER = Color("21292ecc")
const UI_COLOR_WINDOW = Color("21292eff")
const UI_COLOR_BG_TRANSPARTENT = Color("33e8e3ff")
const UI_COLOR_HEADER_TRANSPARTENT = Color("576163cc")
const UI_COLOR_WINDOW_TRANSPARTENT = Color("576163ff")

@export var UI_colors: Array[Color] = [
UI_COLOR,
UI_COLOR_BG,
UI_COLOR_HEADER,
UI_COLOR_WINDOW,
UI_COLOR_BG_TRANSPARTENT,
UI_COLOR_HEADER_TRANSPARTENT,
UI_COLOR_WINDOW_TRANSPARTENT,
]

@export var UI_colors_dict: Dictionary[String, Color] = {
UI_COLOR.to_html() : UI_COLOR,
UI_COLOR_BG.to_html() : UI_COLOR_BG,
UI_COLOR_HEADER.to_html() : UI_COLOR_HEADER,
UI_COLOR_WINDOW.to_html() : UI_COLOR_WINDOW,
UI_COLOR_BG_TRANSPARTENT.to_html() : UI_COLOR_BG_TRANSPARTENT,
UI_COLOR_HEADER_TRANSPARTENT.to_html() : UI_COLOR_HEADER_TRANSPARTENT,
UI_COLOR_WINDOW_TRANSPARTENT.to_html() : UI_COLOR_WINDOW_TRANSPARTENT}
```
The above code defines a few constant colors and then uses them to define an exported Array and Dictionary. The Array works correctly, the Dictionary does not initialize default value properly - it's null. Thus any value, even the default defined in the script, will be stored in the scene. You can't revert the value if the script is `@tool`. If you make it non-tool, the Dictionary gets reverted into null:


It does not matter whether the Dictionary is typed.

### Steps to reproduce

1. Attach the code above to a script
2. Try reverting colors dict

### Minimal reproduction project (MRP)

See above.

No source file or test is named. Start by reproducing the exported Dictionary behavior with the provided GDScript in Godot 4.5 dev1, comparing it with the working exported Array and both @tool and non-tool modes. Done means the Dictionary keeps its declared default and reverting the scene value behaves correctly.

Written by the indexing model from the issue text.