[Kicker] Rename id column to itemColumn

In Qt 5.12 new magic `column` and `row` properties appeared in the delegate's scope, similar to the `index` and `model` (`modelData`) one.
This causes `column` to access that (being always the number zero for this list model) and as such the delegate not having a width and turning invisible.

Differential Revision: https://phabricator.kde.org/D16316