GtkDialog: theme dialog with a black bg and white text
GtkDialog: theme dialog with a black bg and white text

This is coherent with the themeing for Palettes and modal
alerts. Follow up of SL #3971

Signed-off-by: Simon Schampijer <simon@laptop.org
Acked-by: Manuel Quiñones <6f5069c5b6be23302a13accec56587944be09079@laptop.org>

sugarlabs/sugar-artwork,ceibal-tatu/sugar-artwork,ceibal-tatu/sugar-artwork,sugarlabs/sugar-artwork,tchx84/debian-pkg-sugar-artwork,tchx84/debian-pkg-sugar-artwork,samdroid-apps/sugar-artwork,godiard/sugar-artwork,gusDuarte/sugar-artwork,gusDuarte/sugar-artwork,godiard/sugar-artwork,godiard/sugar-artwork,tchx84/debian-pkg-sugar-artwork,samdroid-apps/sugar-artwork,i5o/sugar-artwork,i5o/sugar-artwork,samdroid-apps/sugar-artwork,gusDuarte/sugar-artwork,ceibal-tatu/sugar-artwork,gusDuarte/sugar-artwork,i5o/sugar-artwork,sugarlabs/sugar-artwork