Can't make default attribute works with filepicker

hi,

I can't make default attribute works with filepicker in my blueprint

This is my blueprint :
--- yaml
header.el_preloader_img:
type: filepicker
label: THEME_PRELOADER_IMG
help: THEME_PRELOADER_IMG_HELP
folder: 'theme@:/images/preloader'
preview_images: true
default: preloader.gif
accept:

• .png
• .jpg
• .jpeg

• .gif

Can you please create an issue for this here: https://github.com/getgrav/grav-plugin-admin/issues

@rhukster done here : https://github.com/getgrav/grav-plugin-admin/issues/859