M-SPC is not bound to leader-ket when evil mode is disabled

### I confirm that...

- [X] I have searched the [issue tracker](https://github.com/doomemacs/doomemacs/issues), [documentation](https://docs.doomemacs.org), [FAQ](https://docs.doomemacs.org/-/faq), [Discourse](https://discourse.doomemacs.org), and [Google](https://google.com), in case this issue has already been reported/resolved.

- [X] I have read "[How to Debug Issues](https://doomemacs.org/d/how2debug)", and will use it to provide as much information about this issue as possible.

- [X] The issue can be reproduced on the **latest** available commit of Doom.

- [X] The issue can be reproduced on a stable release of Emacs, such as 27 or 28. *(Doom does not support development builds like 29+ or any version ending in .50 or .9x)*

### Expected behavior

When I disable evil-mode temporarily with `C-z`, then the leader-key is mapped to `M-SPC` instead of `SPC`, just like in evil input mode.

When I disable evil mode, either via `M-x evil-mode` or by commenting it in `init.el`, I'd expect the leader key to be on `M-SPC` as well.

### Current behavior

When evil-mode is fully disabled, `M-SPC` is mapped to `just one space` (in simple.el) rather than to the leader-key - according to `describe-key`.

The leader-key menu is not accessible anymore.

### Steps to reproduce

1. Open Emacs
2. Disable evil mode `M-x evil-mode`
3. Type `M-SPC`

### System Information

https://pastebin.com/TjfxqnKm