collection-box: Make stack background solid
GtkStack doesn't have any background by default. If it has a non-revealed GtkInfoBar just above it, its border can be visible. Add a background to prevent this.
Fixes #162 (closed)
GtkStack doesn't have any background by default. If it has a non-revealed GtkInfoBar just above it, its border can be visible. Add a background to prevent this.
Fixes #162 (closed)