PC3: Fix ItemDelegate's padding for non-default background
PC3: Fix ItemDelegate's padding for non-default background
In particular, fix ListSectionHeader which has no background at all.
This patch does not require a qqc2-desktop-style counterpart, since there ItemDelegate does not depend on its background's properties.
PlasmaExtras/ListSectionHeader: Delete empty background completely
Bare Item does not help anyone, as demonstrated in the previous patch which fixed ItemDelegate's padding from exploding with tons of errors.