Error on Facebook.php – Line 189

Facebook_Loader::async_script_loader_src processes the script_loader_src filter applied in wp-includes/class.wp-scripts.php:

apply_filters( 'script_loader_src', $src, $handle )

The Facebook plugin for WordPress adds itself to the filter at priority 1 with two accepted args: the $src and $handle parameters from the applied filter.

Is it possible you have other plugins acting on the script_loader_src filter that could be causing the error?

I just deactivated all plug-ins. Then proceeded to activate the Facebook plug-in. The same error is occurring.