Closing empty tabs after download (#2510)

Task/Issue URL:
https://app.asana.com/0/1177771139624306/1206835038894671/f

**Description**:
Fix of empty tabs remaining in the tab bar after a download finishes.

DuckDuckGo/Tab/TabExtensions/DownloadsTabExtension.swift

@@ -213,16 +213,23 @@ extension DownloadsTabExtension: NavigationResponder {
     func enqueueDownload(_ download: WebKitDownload, withNavigationAction navigationAction: NavigationAction?) {
         let task = downloadManager.add(download, fromBurnerWindow: self.isBurner, delegate: self, destination: .auto)
 
+        var isMainFrameNavigationActionWithNoHistory: Bool {
+            guard let navigationAction,
+                  navigationAction.isForMainFrame,
+                  navigationAction.isTargetingNewWindow,
+                  // webView has no navigation history (downloaded navigationAction has started from an empty state)
+                  (navigationAction.redirectHistory?.first ?? navigationAction).fromHistoryItemIdentity == nil
+            else { return false }
+            return true
+        }
+
         // If the download has started from a popup Tab - close it after starting the download
         // e.g. download button on this page:
         // https://en.wikipedia.org/wiki/Guitar#/media/File:GuitareClassique5.png
-        guard let navigationAction,
-              navigationAction.isForMainFrame,
-              navigationAction.isTargetingNewWindow,
-              let webView = download.webView,
-              // webView has no navigation history (downloaded navigationAction has started from an empty state)
-              (navigationAction.redirectHistory?.first ?? navigationAction).fromHistoryItemIdentity == nil
-        else { return }
+        guard let webView = download.webView,
+              isMainFrameNavigationActionWithNoHistory
+                // if converted from navigation response but no page was loaded
+                || navigationAction == nil && webView.backForwardList.currentItem == nil else { return }
 
         self.closeWebView(webView, afterDownloadTaskHasStarted: task)
     }