WP_PAGENAVI Error - Archive Page

<?php get_header(); ?>

        <div class="l-inside">
                <article class="l-constrained">

                        <?php
                                $arc_year = get_the_time('Y');
                                $arc_month = get_the_time('m');
                                $posts = query_posts( "year=$arc_year&monthnum=$arc_month" );
                                $count = count($posts);
                        ?>

                        <h2>
                                Archive Results for <a href="<?php echo get_month_link($arc_year, $arc_month); ?>">"<?php the_time('F Y'); ?>"</a> <?php echo $count ?> Results Found
                        </h2>


                        <?php if ( have_posts() ) while ( have_posts() ) : the_post(); ?>

                        <section class="over-fix sub-header">
                                <div class="postdate">
                                        <div class="date">
                                                <?php echo get_the_date('d M'); ?>
                                        </div>
                                </div>
                                <div class="title switch-links">
                                        <h1><a href="<?php the_permalink(); ?>" alt="<?php the_title_attribute(); ?>"><?php the_title();?></a></h1>
                                </div>
                                <div>
                        <a class="button" href="<?php the_permalink() ?>" title="<?php the_title_attribute(); ?>">Read More…</a>

                                </div>
                        </section>

                        <?php endwhile; ?>

                        <?php wp_pagenavi(); ?>

                </article>

                <?php get_sidebar(); ?>
        </div>
<?php get_footer(); ?>