Most likely you have installed a plugin for adding posts ( one click post Maybe)
Here is how to get rid of that error.
1-open you PHPMyadmin ( your MySQL database from your hosting control )
2-Look up a table called “wp_bp_notifications”
3-in that table look under the column “component_name”, delete the entire row of any field you find empty under that column
This should fix your problem, please let me know if you have any questions
