...

src/calibre/gui2/tweak_book/boss.py

@@ -61,7 +61,7 @@ class Boss(QObject):
         if not dirtied:
             return True
         return question_dialog(self.gui, _('Unsaved changes'), _(
-            'You have unsaved changes in the files %s. If you proceeed,'
+            'You have unsaved changes in the files %s. If you proceed,'
             ' you will lose them. Proceed anyway?') % ', '.join(dirtied))
 
     def open_book(self, path=None):

src/calibre/utils/ipc/simple_worker.py

@@ -263,6 +263,9 @@ def offload():
             res = {'result':None, 'tb':None}
             try:
                 mod, func, args, kwargs = args
+                if mod is None:
+                    eintr_retry_call(conn.send, res)
+                    continue
                 f = func_cache.get((mod, func), None)
                 if f is None:
                     try: