,Tower Defense - How to set it so that i cannot block myself in when creating Tower Bases?

In My Tower Defense game i want to have it set up so that i cant place a tower base while there are no valid spaces to move through, currently i dont have Ai running anywhere in the game (not sure if this is a problem but will have Ai eventually). I just want to know if there is a way in blueprints to check to see if there is or isnt a valid open space.
I am spawning the Tower Bases (actors) with line trace.