Undefined property notice: stdClass::$performanceMetrics

Problem/Motivation

After executing a search, the following notices are displayed on the search results page:

Notice: Undefined property: stdClass::$performanceMetrics in Funnelback\Response->__construct() (line 93 of C:\wamp\drupalbootstrap\drupal\sites\all\modules\funnelback\src\Funnelback\Response.php).
Notice: Trying to get property of non-object in Funnelback\Response->__construct() (line 93 of C:\wamp\drupalbootstrap\drupal\sites\all\modules\funnelback\src\Funnelback\Response.php).
Notice: Undefined property: stdClass::$performanceMetrics in Funnelback\Response->__construct() (line 93 of C:\wamp\drupalbootstrap\drupal\sites\all\modules\funnelback\src\Funnelback\Response.php).
Notice: Trying to get property of non-object in Funnelback\Response->__construct() (line 93 of C:\wamp\drupalbootstrap\drupal\sites\all\modules\funnelback\src\Funnelback\Response.php).

Proposed resolution

Test for the existence of $response->performanceMetrics->totalTimeMillis and set $this->totalTimeMillis to NULL if not available.