[imgui] Second imgui UI window breaks focus/input

[andrei8l]

Describe the bug

Both keyboard and mouse input is generally broken when/after showing two imgui windows.

Attach save file

N/A

Steps to reproduce

1. Press ? to show the keybindings UI
2. Press ? again to show another one
3. Press ESC to close the second one
4. Can't use the remaining UI with the keyboard anymore

Similar issue:

1. Open a popup (ex: wait, then interrupt)
2. Press ?
3. Focus keeps switching back to the popup, making the keybindings UI unusable

Expected behavior

Functional layering

Screenshots

N/A

Versions and configuration

• OS: Linux
  • OS Version: LSB Version: n/a; Distributor ID: Arch; Description: Arch Linux; Release: rolling; Codename: n/a;
• Game Version: cdda-experimental-2024-03-24-0121 cf9267f [64-bit]
• Graphics Version: Tiles
• Game Language: System language []
• Mods loaded: [
  Dark Days Ahead [dda],
  Disable NPC Needs [no_npc_food],
  Portal Storms Ignore NPCs [personal_portal_storms],
  Slowdown Fungal Growth [no_fungal_growth]
  ]

Additional context

N/A