From de9a1a8ca2912f8c280587a9bd6758965dda2a01 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sat, 8 May 2021 16:35:21 +0530
Subject: [PATCH] Fix #1927818 [Private
 bug](https://bugs.launchpad.net/calibre/+bug/1927818)

---
 src/calibre/gui2/tweak_book/boss.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index 04a7d15d9b..1cb7121f6e 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -667,6 +667,8 @@ class Boss(QObject):
             self.rewind_savepoint()
 
     def manage_fonts(self):
+        if not self.ensure_book(_('No book is currently open. You must first open a book to manage fonts.')):
+            return
         self.commit_all_editors_to_container()
         self.gui.manage_fonts.display()