Overriding workbench.colorCustomizations does not work

[etienne-dldc]

Describe the bug

When defining a workbench.colorCustomizations object in slides.vscodeSettings before activating slide mode it does not work.
The default workbench.colorCustomizations from the extension is removed but the custom one is not added...

How to reproduce

Activate the slides mode with this .vscode/settings.json

{
  "slides.vscodeSettings": {
    "workbench.colorCustomizations": {
      "editorCursor.background": "#ffffff",
      "editorCursor.foreground": "#0000bb",
      "editor.lineHighlightBackground": "#0e121b15",
      "editor.selectionBackground": "#aaeeff",
      "editorError.background": "#ff000050",
      "editorError.foreground": "#fe0101",
      "editorError.border": "#fe0101"
    }
  }
}

Expected behavior

The workbench.colorCustomizations defined in slides.vscodeSettings should be in the slide mode.

Additional information

• Version of the extension impacted: _ v4.2.1_