Timeline error

I have some Javascript error on my website. Users can't comment or load comments on timeline. 

My error log shows this. Who can help please.. LeonidS 

Fatal error: Uncaught Error: Call to a member function genDbCacheKey() on null in /home/zealnutc/public_html/inc/classes/BxDolLiveUpdates.php:181

Stack trace:

#0 /home/zealnutc/public_html/inc/classes/BxDolLiveUpdates.php(188): BxDolLiveUpdates->_getCacheInfo()

#1 /home/zealnutc/public_html/inc/classes/BxDolLiveUpdates.php(216): BxDolLiveUpdates->_getCached('systems')

#2

/home/zealnutc/public_html/inc/classes/BxDolLiveUpdates.php(102): BxDolLiveUpdates->_getCachedSystems()

#3 /home/zealnutc/public_html/live_updates.php(16): BxDolLiveUpdates->perform()

#4 {main}

thrown in /home/zealnutc/public_html/inc/classes/BxDolLiveUpdates.php on line 181