Check within the browser that callsign is provided before submitting the form

application/views/qso/index.php

@@ -69,7 +69,7 @@
               <!-- Callsign Input -->
               <div class="form-group">
                 <label for="callsign">Callsign</label>
-                <input type="text" class="form-control" id="callsign" name="callsign">
+                <input type="text" class="form-control" id="callsign" name="callsign" required>
                 <small id="callsign_info" class="form-text text-muted"></small>
               </div>
 

assets/css/general.css

@@ -72,6 +72,13 @@
     border: none;
 }
 
+input:invalid {
+  box-shadow: 0 0 5px 1px red;
+}
+
+input:focus:invalid {
+  box-shadow: none;
+}
 
 TD.eqsl{
     width: 33px;