### Godot version

4.1 beta2

### System information

Windows 10 Home

### Issue description

I had a control with a custom theme which i removed. When loading the project again the Theme Editor is opened and some actions, like Show Default or Override All, cause the editor to crash.

### Steps to reproduce

1. create a scene with a Control node
2. add a custom theme to it
3. click the theme so the Theme Editor opens
4. remove the theme
5. save the scene
6. close the project and open it again (Theme Editor needs to be opened when closing the project)
7. click Show Default or Override All

### Minimal reproduction project

[Godot41_themeEditorCrash.zip](https://github.com/godotengine/godot/files/11760454/Godot41_themeEditorCrash.zip)

/* There are three different formulas for the conversion from normalized
	 * values to relative decibal values.
	 * One formula is an exponential graph which intends to counteract
	 * the logarithmic nature of human hearing. This is an approximation
	 * of the behavior of a 'logarithmic potentiometer' found on most
	 * musical instruments and also emulated in popular software.
	 * The other two equations are hand-tuned linear tapers that intend to
	 * try to ease the exponential equation in areas where it makes sense.*/
	if (normalized > 0.6f) {
		return 22.22f * normalized - 16.2f;
	} else if (normalized < 0.05f) {
		return 830.72 * normalized - 80.0f;
	} else {
		return 45.0f * Math::pow(normalized - 1.0, 3);
	}
}
float EditorAudioBus::_scaled_db_to_normalized_volume(float db) {