fix: If there was no chat description, and it's set to be an empty string, don't send out a "chat description changed" message (#7879)

fix #7877

The bug was: If there is no chat description, and the chat description
is set to an empty string, the INSERT statement inserted a row with an
empty chat description, and therefore from the view of the INSERT
statement, something changed.

This PR fixes this by simply loading the chat description first, and
comparing it.

src/chat/chat_tests.rs

@@ -3269,6 +3269,36 @@ async fn test_chat_description(initial_description: &str, join_via_qr: bool) ->
     Ok(())
 }
 
+/// Tests explicitly setting an empty chat description
+/// doesn't trigger sending out a message
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_setting_empty_chat_description() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = &tcm.alice().await;
+    let bob = &tcm.bob().await;
+
+    tcm.section("Create a group chat, and add Bob in order to promote it");
+    let alice_chat_id = create_group(alice, "My Group").await?;
+
+    add_contact_to_chat(
+        alice,
+        alice_chat_id,
+        alice.add_or_lookup_contact_id(bob).await,
+    )
+    .await?;
+    let _hi = alice.send_text(alice_chat_id, "hi").await;
+
+    set_chat_description(alice, alice_chat_id, "").await?;
+    assert!(
+        alice
+            .pop_sent_msg_opt(Duration::from_secs(0))
+            .await
+            .is_none()
+    );
+
+    Ok(())
+}
+
 /// Tests that directly after broadcast-securejoin,
 /// the brodacast is shown correctly on both devices.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]