BOOL value behaviour with high optimization level

viewController.m

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    BOOL isMember = NO; // here must be variable set to no, otherwise is initialized to thrash
    
    for (NSIndexPath *ip in self.expandedCells) {
        if ([ip isEqualToIndexPath:indexPath]) {
            isMember = YES;
            break;
        }
    }
    
    if (isMember) {
        [self.expandedCells removeObject:indexPath];
    } else {
        [self.expandedCells addObject:indexPath];
    }
    
    [tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
}