Fix id_token KeyError on OAuth2 logout.

web/pgadmin/authenticate/oauth2.py

@@ -69,7 +69,6 @@ def init_app(app):
                      methods=['GET', 'POST'])
     @pgCSRFProtect.exempt
     def oauth_logout():
-        id_token = session['oauth2_token']['id_token']
         logout_url = None
         if 'oauth2_logout_url' in session:
             logout_url = session['oauth2_logout_url']
@@ -81,6 +80,7 @@ def init_app(app):
 
         logout_user()
         if logout_url:
+            id_token = session['oauth2_token'].get('id_token')
             return redirect(logout_url.format(
                 redirect_uri=request.url_root,
                 id_token=id_token))