How to edit header for a description meta tag?

I’m using the Stargazer theme in wordpress which allows me to choose whether to display header text or not under Appearance > Header.

I chose to not display header text on the webiste by unchecking the option. The problem I have is that by turning this option off, the website doesn’t have a meta description in the header which is kind of needed for SEO purposes. Is there a way around this? Here’s the code in the header.php which I have left untouched for now..

<?php if ( display_header_text() ) : // If user chooses to display header text. ?>

					<div id="branding">
						<?php hybrid_site_title(); ?>
						<?php hybrid_site_description(); ?>
					</div><!-- #branding -->

				<?php endif; // End check for header text. ?>

				<?php hybrid_get_menu( 'secondary' ); // Loads the menu/secondary.php template. ?>

			</header><!-- #header -->

			<?php if ( get_header_image() && !display_header_text() ) : // If there's a header image but no header text. ?>

				<a href="<?php echo home_url(); ?>" title="<?php echo esc_attr( get_bloginfo( 'name' ) ); ?>" rel="home"><img class="header-image" src="<?php header_image(); ?>" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="" /></a>

			<?php elseif ( get_header_image() ) : // If there's a header image. ?>

				<img class="header-image" src="<?php header_image(); ?>" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="" />

			<?php endif; // End check for header image. ?>