[simple-scan/cherry-pick-cd091da8] Don't ask for saving Pages, if there is nothing to save

[Bartosz <bkosiorek src gnome org>]

commit 88e01199b8a961ca921ef068793bce8c37eae8e2
Author: Bartosz Kosiorek <gang65 poczta onet pl>
Date:   Wed Dec 4 00:35:29 2019 +0000

    Don't ask for saving Pages, if there is nothing to save
    
    
    (cherry picked from commit cd091da824914c63c6698d251c7d3aa39b50ad65)

 src/app-window.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/app-window.vala b/src/app-window.vala
index 3ec49be..1cd14f4 100644
--- a/src/app-window.vala
+++ b/src/app-window.vala
@@ -539,7 +539,7 @@ public class AppWindow : Gtk.ApplicationWindow
 
     private async bool prompt_to_save_async (string title, string discard_label)
     {
-        if (!book_needs_saving)
+        if (!book_needs_saving || (book.n_pages == 0))
             return true;
 
         var dialog = new Gtk.MessageDialog (this,