1px branch lines are shown in QTreeView even with 0px indentation.

When there is a 0px identation set with setIndentation(0), no tree branches should be visible.

Currently, when the identation is set to 0px, there are 1px tree branches at the left of the items, and they look like a visual artifact.

If someone sets identation to 0px, he clearly doesn't want to see tree branches, especially if they don't look like tree branches.

The only way to fix this from the application (disable branches) is to override QTreeView::drawBranches. See https://git.reviewboard.kde.org/r/105342/

Disabling tree branches when the identation is 0px won't break anything, because they are not useful when they are only 1px wide.