It appears there is a problem in the experience addon.
slp-experience/include/module/ui/SLP_Experience_UI.php, LINE 751, $this->addon can be null.
Fix required the addon property be removed from the class, and in store-locator-le/include/base_class.userinterface.php, the addon property needed to be private such that SLPlus_BaseClass_Object::__get would work.
Could you provide your plugin environment for this post. I.e A screenshot of SLP plugin environment would show us the versions you are using.
The developer requires this information whenever I report to him. I have not seen the error when updated SLP base plugin and Power and Experience but I may have different configuration.