Run behavior tree not setting Path node

Hello Everyone I am following the basics of AI video of unreal engine 4

[Basics of AI | Live Training | Unreal Engine - YouTube][1]

by Shadden .At 37:54 he tells that Run Behavior Tree node should be at the beginning and if we don’t do it then the path node would be none ,but he didn’t give any reason .So my question is why did he do that?I mean the run behavior tree node should run after the value has been set .

and Also at 30:48 he experiences the crash with editor.I am also experiencing the same problem in 4.8.6 so is the bug still not fixed ?

Try leaving “Run Behavior Tree” at the end and put a “Use Blackboard” right after the Event BeginPlay.