Fix bug in deleting account selected in preferences

src/cutecoin/core/app.py

@@ -109,6 +109,9 @@ class Application(QObject):
             self.current_account = None
         with open(config.parameters['data'], 'w') as outfile:
             json.dump(self.jsonify(), outfile, indent=4, sort_keys=True)
+        if self.preferences['account'] == account.name:
+            self.preferences['account'] = ""
+            self.save_preferences(self.preferences)
 
     def change_current_account(self, account):
         '''