Reapply "17466 FIX Refresh user messages not only on page reload"

This reverts commit 2e8394e.

SUP-21044

Change-Id: Ieaa3a7cf3f92bd41bcb959b31676610e5f77019f

.werks/17466.md

@@ -0,0 +1,18 @@
+[//]: # (werk v2)
+# Refresh user messages not only on page reload
+
+key        | value
+---------- | ---
+date       | 2025-01-07T12:09:20+00:00
+version    | 2.4.0b1
+class      | fix
+edition    | cre
+component  | multisite
+level      | 1
+compatible | yes
+
+Messages send via "Setup" - "Users" - "Send user messages" were only shown on
+page reload.
+
+New messages of methods "Show popup message" and "Show hint in the 'User' menu"
+are now shown on every sidebar status update (default: 30 seconds).

packages/cmk-frontend/src/js/modules/sidebar.ts

@@ -693,8 +693,7 @@ export function execute_sidebar_scheduler() {
     }
 
     if (g_sidebar_notify_interval !== null) {
-        const timestamp = new Date().getTime() / 1000;
-        if (timestamp % g_sidebar_notify_interval == 0) {
+        if (g_seconds_to_update == 0) {
             update_messages();
             if (g_may_ack) {
                 update_unack_incomp_werks();
@@ -1248,18 +1247,22 @@ function update_messages() {
 }
 
 export function update_message_trigger(msg_text: string, msg_count: number) {
-    const l = document.getElementById("messages_label")!;
-    if (msg_count === 0) {
-        l.style.display = "none";
-        return;
-    }
+    const l = document.getElementById("messages_label");
+    if (l) {
+        if (msg_count === 0) {
+            l.style.display = "none";
+            return;
+        }
 
-    l.innerText = msg_count.toString();
-    l.style.display = "inline";
+        l.innerText = msg_count.toString();
+        l.style.display = "inline";
+    }
 
-    const user_messages = document.getElementById("messages_link_to")!;
-    const text_content = msg_count + " " + msg_text;
-    user_messages.textContent = text_content;
+    const user_messages = document.getElementById("messages_link_to");
+    if (user_messages) {
+        const text_content = msg_count + " " + msg_text;
+        user_messages.textContent = text_content;
+    }
 }
 
 function mark_message_read(