Post Feed with option to specify category

<?php if ( get_field( 'category_slug_name' ) ): ?>
	<h1 class="page-title"><?php the_field('feed_list_title'); ?></h1>
		<ul>
			<?php
			global $post;
			$args = array( 'numberposts' =>get_field('number_of_excerpts'), 'offset'=> 0, 'category_name' =>get_field('category_slug_name'), 'orderby' => 'post_date', 'order' => 'DSC');
			$myposts = get_posts( $args );
			foreach( $myposts as $post ) :	setup_postdata($post); ?>
								<li>
								<div class="clear">
								<div class="feed-thumbs">
								<a href="<?php the_permalink(); ?>" rel="bookmark">
								<?php if ( has_post_thumbnail() ) {
								the_post_thumbnail('medium');
								} else { ?>
								<img src="<?php bloginfo('template_directory'); ?>/images/default_thumbnail.jpg" alt="<?php the_title(); ?>" />
								<?php } ?>
								</a>
								</div><!--ends 4-thumbs -->
								<div class="feed-excerpt">
								<h3><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h3>
								<?php the_excerpt();?>
								<p class="archive-link"><a href="<?php the_permalink(); ?>" rel="bookmark">read more</a></p>
								</div><!-- ends front-excerpt -->
								
								</div><!-- ends clear-->
								</li>
								<hr/>
			<?php endforeach; ?>
		</ul>
<?php else: // field_name returned false ?>	
<!--if no entry in field query will show posts unfiltered by category -->	
			<?php 
			// the query
			$wpb_all_query = new WP_Query(array('post_type'=>'post', 'post_status'=>'publish', 'posts_per_page'=>6)); ?>
			<h1 class="page-title"><?php the_field('feed_list_title'); ?></h1>
			<ul>
				<!-- the loop -->
				<?php while ( $wpb_all_query->have_posts() ) : $wpb_all_query->the_post(); ?>
					<li>
					<div class="clear">
					<div class="feed-thumbs">
					<a href="<?php the_permalink(); ?>" rel="bookmark">
					<?php if ( has_post_thumbnail() ) {
					the_post_thumbnail('medium');
					} else { ?>
					<img src="<?php bloginfo('template_directory'); ?>/images/default_thumbnail.jpg" alt="<?php the_title(); ?>" />
					<?php } ?>
					</a>
					</div><!--ends 4-thumbs -->
					<div class="feed-excerpt">
					<h3><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h3>
					<?php the_excerpt();?>
					<p class="archive-link"><a href="<?php the_permalink(); ?>" rel="bookmark">read more</a></p>
					</div><!-- ends front-excerpt -->
					</div><!-- ends clear-->					
					</li>
					<hr/>
				<?php endwhile; ?>
				<!-- end of the loop -->
			</ul>
<?php endif; // end of if field_name logic ?>	
<?php wp_reset_postdata(); ?>