Fix custom document title override using setDocumentTitle (close #1317)

PR #1318

Author: marcin-j

common/changes/@snowplow/browser-tracker-core/marcin-j-master_2024-06-18-05-25.json

@@ -0,0 +1,10 @@
+{
+    "changes": [
+      {
+        "packageName": "@snowplow/browser-tracker-core",
+        "comment": "Fix custom document title override using setDocumentTitle (#1317)",
+        "type": "none"
+      }
+    ],
+    "packageName": "@snowplow/browser-tracker-core"
+  }

libraries/browser-tracker-core/src/tracker/index.ts

@@ -987,7 +987,7 @@ export function Tracker(
 
       // So we know what document.title was at the time of trackPageView
       lastDocumentTitle = document.title;
-      lastConfigTitle = title;
+      lastConfigTitle = title ?? lastConfigTitle;
 
       // Fixup page title
       const pageTitle = fixupTitle(lastConfigTitle || lastDocumentTitle);