Label color swatches "Quick Load" results in editor freezes and frequent crashes

### Tested versions

Happens frequently in: **v4.6.2.stable.mono.official [71f334935]**

### System information

Godot v4.6.2.stable.mono - Windows 11 (build 26200) - Multi-window, 2 monitors - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4070 Ti (NVIDIA; 32.0.15.8180) - AMD Ryzen 7 7700X 8-Core Processor (16 threads) - 31.14 GiB memory

### Issue description

When using a `Label` -> `LabelSettings` -> `Color` -> `Swatches` property (maybe not just limited to `Label`) and using `Quick Load` to load a resource, the editor will hang for 10-15 seconds, or freeze entirely, resulting in a Godot Editor crash.

This may or may not be related to whether the `LabelSettings` resource is saved locally before trying to Quick Load a swatch (this is a guess).

### Steps to reproduce

- Create a new `Label` node
- Create a new `Label Settings` resource (saved or `inline`?)
- Go to `Font` -> `Color` -> `Swatches`
- Show all options (three dots button)
- Quick load a local swatch resource file (`*.tres`)
- Frequent chance of the Godot editor hang for 10-15-20 seconds or freezing and crashing

### Minimal reproduction project (MRP)

This is an intermittent problem, not deterministic, but frequent enough to create this bug report.

Start by reproducing the reported Inspector path: Label → LabelSettings → Color → Swatches, then use the three-dots menu to Quick Load a local .tres swatch resource. Compare saved and inline LabelSettings resources, since the report identifies this as a possible factor. Done means the editor no longer hangs or crashes during this workflow; no source file or regression test is named in the report.

Written by the indexing model from the issue text.