Refresh the db when on_device is refreshed only if composite columns are defined.

src/calibre/gui2/library/models.py

@@ -125,7 +125,7 @@ def set_device_connected(self, is_connected):
 
     def refresh_ondevice(self):
         self.db.refresh_ondevice()
-        self.refresh(reset=False)
+        self.resort()
         self.research()
 
     def set_book_on_device_func(self, func):

src/calibre/library/caches.py

@@ -914,6 +914,8 @@ def count(self):
         return len(self._map)
 
     def refresh_ondevice(self, db):
+        if self.composites:
+            self.refresh(db)
         ondevice_col = self.FIELD_MAP['ondevice']
         for item in self._data:
             if item is not None: