PHP errors

Having this repeated issue in my php log file. any assistance would be great

[09-Feb-2019 18:44:30 UTC] PHP Notice:  Undefined index: onclick in /home/public_html/cache/bx_templ_en_protean_28f348cb9be842b990a83e890ca77651.php on line 7

[09-Feb-2019 18:44:33 UTC] PHP Fatal error:  Uncaught Error: Call to a member function genDbCacheKey() on null in /home/public_html/inc/classes/BxDolLiveUpdates.php:190

Stack trace:

#0 /home/public_html/inc/classes/BxDolLiveUpdates.php(197): BxDolLiveUpdates->_getCacheInfo()

#1 /home/public_html/inc/classes/BxDolLiveUpdates.php(225): BxDolLiveUpdates->_getCached('systems')

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

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

#4 {main}

  thrown in /home/public_html/inc/classes/BxDolLiveUpdates.php on line 190