Do nothing on empty input

application/views/visitor/layout/footer.php

@@ -253,6 +253,14 @@
                $('[class*="buttons"]').css("color", "white");
             }
         </script>
+        <script type="text/javascript">
+            function validateForm() {
+                let x = document.forms["searchForm"]["callsign"].value;
+                if (x == "") {
+                    return false;
+                }
+            }
+        </script>
     <?php } ?>
 
   </body>

application/views/visitor/layout/header.php

@@ -77,7 +77,7 @@
 		<?php if (!empty($slug)) {
 			$this->CI =& get_instance();
 			if ($this->CI->public_search_enabled($slug) || $this->session->userdata('user_type') >= 2) { ?>
-				<form method="post" action="<?php echo site_url('visitor/search'); ?>" class="form-inline">
+				<form method="post" name="searchForm" action="<?php echo site_url('visitor/search'); ?>" onsubmit="return validateForm()" class="form-inline">
 				<input class="form-control mr-sm-2" id="searchcall" type="search" name="callsign" placeholder="<?php echo lang('menu_search_text'); ?>" <?php if (isset($callsign) && $callsign != '') { echo 'value="'.strtoupper($callsign).'"'; } ?> aria-label="Search">
 					<input type="hidden" name="public_slug" value="<?php echo $slug; ?>">
 					<button class="btn btn-outline-success my-2 my-sm-0" type="submit"><i class="fas fa-search"></i> <?php echo lang('menu_search_button'); ?></button>