fancy-splash-apply-appropriate-image in doom-load-theme hook causes format error.

[Schievel1]

When I activate

(add-hook 'doom-load-theme-hook #'fancy-splash-apply-appropriate-image)

I get

⛔ Error (doom-load-theme-hook): Error running hook "fancy-splash-apply-appropriate-image" because: (error Format specifier doesn’t match argument type)
⛔ Error (doom-init-ui-hook): Error running hook "+doom-dashboard-init-h" because: (error Format specifier doesn’t match argument type)

at startup.

Strangely enough this does not happen when I do /usr/bin/emacs --debug-init.

When only

(add-hook 'window-size-change-functions #'fancy-splash-apply-appropriate-image)

is active, it works fine.