...

src/calibre/gui2/preferences/plugins.ui

@@ -76,6 +76,10 @@
      <property name="text">
       <string>&amp;Add a new plugin</string>
      </property>
+     <property name="icon">
+      <iconset resource="../../../../resources/images.qrc">
+       <normaloff>:/images/plugins.png</normaloff>:/images/plugins.png</iconset>
+     </property>
     </widget>
    </item>
   </layout>

src/calibre/gui2/shortcuts.py

@@ -150,7 +150,7 @@ class Delegate(QStyledItemDelegate):
         custom = []
         if editor.custom.isChecked():
             for x in ('1', '2'):
-                sc = getattr(editor, 'shortcut'+x)
+                sc = getattr(editor, 'shortcut'+x, None)
                 if sc is not None:
                     custom.append(sc)
 
@@ -266,6 +266,11 @@ class ShortcutConfig(QWidget):
         self.view.scrollTo(index)
 
 
+    @property
+    def is_editing(self):
+        return self.view.state() == self.view.EditingState
+
+
 if __name__ == '__main__':
     from calibre.gui2 import is_ok_to_use_qt
     from calibre.gui2.viewer.keys import SHORTCUTS

src/calibre/gui2/viewer/documentview.py

@@ -120,6 +120,13 @@ class ConfigDialog(QDialog, Ui_Dialog):
 
 
     def accept(self, *args):
+        if self.shortcut_config.is_editing:
+            from calibre.gui2 import info_dialog
+            info_dialog(self, _('Still editing'),
+                    _('You are in the middle of editing a keyboard shortcut'
+                        ' first complete that, by clicking outside the '
+                        ' shortcut editing box.'), show=True)
+            return
         c = config()
         c.set('serif_family', unicode(self.serif_family.currentFont().family()))
         c.set('sans_family', unicode(self.sans_family.currentFont().family()))