Minor discord cl fix (#23833)

This means it won't send a dummy post if no changelog entries are found. The old one just sent it and didn't check if it worked.

Tools/actions_changelogs_since_last_run.py

@@ -125,6 +125,10 @@ def send_to_discord(entries: Iterable[ChangelogEntry]) -> None:
                 else:
                     content.write(f"{emoji} - {message}\n")
     
+    if count == 0:
+        print("Skipping discord push as no changelog entries found")
+        return
+
     print(f"Posting {count} changelog entries to discord webhook")
 
     body = {