BAD blueprint image appears when I drop an assets

I had problem that whene ever I drop the AI citizens (BP_CitizensGenerator_01), it appears an image which includes a text said ( BLUEPRINT BAD)
can someone tell me why this appears, I am working on my graduation project using UE4

This is usually to tell you something has gone wrong in compiling or the construction of your BP, its tricky to know what else is going on without more information. Id say have a hunt around and check the BP Compile Results tab for any details on what might be causing the issue.