Hide relay tab on webUI for devices without relays

code/espurna/relay.ino

@@ -367,6 +367,10 @@ void _relayWebSocketUpdate() {
 
 void _relayWebSocketOnSend(JsonObject& root) {
 
+    if (relayCount() == 0) return;
+
+    root["relayVisible"] = 1;
+    
     // Statuses
     JsonArray& relay = root.createNestedArray("relayStatus");
     for (unsigned char relayID=0; relayID<relayCount(); relayID++) {

code/html/index.html

@@ -98,7 +98,7 @@
                             <a href="#" class="pure-menu-link" data="panel-ntp">NTP</a>
                         </li>
 
-                        <li class="pure-menu-item">
+                        <li class="pure-menu-item module module-relay">
                             <a href="#" class="pure-menu-link" data="panel-relay">SWITCHES</a>
                         </li>