Update[9/19/17]: Old answer doesn't work for me anymore in iOS 11. Thanks Apple. The following did:
self.tableView.sectionHeaderHeight = UITableViewAutomaticDimension;
self.tableView.estimatedSectionHeaderHeight = 20.0f;
self.tableView.contentInset = UIEdgeInsetsMake(-18.0, 0.0f, 0.0f, 0.0);
Previous Answer:
As posted in the comments by Chris Ostomo the following worked for me:
- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section
{
return CGFLOAT_MIN; // to get rid of empty section header
}