Lot of "Accessed None" errors with 4.15.2

Hello everyone !

It’s my first post in this forum so the most important thing :
thank you to all of you, your community always been a big help in my work, just from reading you.

With my students, we are working on a big project since the beginning of the year, so we started on 4.13.

We updated unreal to 4.15.2 and now, the project isn’t working because of lots of errors inside the Level Blueprint :

“accessed none trying to read property”


It seems like the level blueprint do not find any direct reference to objects in my scene.

So instead of this


I have to do this

2017-05-13 17_24_45-Level01_ - Level Blueprint Editor.png

Any ideas about this problem ?

I can’t find any information about this anywhere, and we simply don’t have the time to modify every script.

We could rollback to 4.15.1… but… we are VERY curious about all this :slight_smile:

Thank you, again !

What happens when you drag and drop the pointLight3 from the scene within the level blueprint?

Doing this create a reference just like it should, but I cannot access it. At runtime, nothing happens and I have the “accessed none” error.

Does it work if you replace your Light with another Light and then create the reference in your Level Blueprint?

I understand it’s not a valid workaround if you have douzains of lights, but it would help us tackle the problem.

If you’re getting all actor of one light class, it means you have several light blueprint class, am I right?

Exact same thing if I replace with a new light.

I have only one pointlight3 BP, I used a get all actor of class just to see if it works.

The whole project is broken, everything using a direct reference (lights on this exemple, but same problem for level sequence reference which wont play, etc etc etc.)

If I do from scratch, on a new project, something as simple as overlapping trigger -> toggle light visibility (just like the very basics tutorial) - it doesn’t work!!

It looks like a bug.

You should report it with the reproduction steps you’ve provided here.

In the meantime, you could use a workaround and don’t code in the Level Blueprint (but as a teacher I understand you might walk away from the path you’ve chosen).

This is weird that I can’t find any info on this anywhere. Same problem on 4.16 (preview 3).

Can you confirm that it works for you on 4.15.2 or 4.16 ? (level BP with direct references to scene objects)

OK there is something new :

If I create a new level and do something simple with a direct reference, it work :

Then I just Save the map, give it a name (newmap) and BAM, after this it doesnt work.

Really weird

Maybe is it because they are light components and they are tied to the lightning build. Maybe it says “no” because lightning has not been built. What do you say? And the bug happens after you copy / paste a map (a for some reason the lightning build is not copied and paster with it).

nope, the bug concerns everything, any object, not only lights.

Same problems with dynamics lights. It seems to be a problem with map referencing or something.

I just tested in 4.15.2 with a simple cube in the scene (from the Level Blueprint). Every 0.2 seconds I move it by 50 in Z and I have no null ref issue.

I restarted the editor and still no error.

Ok I think we found a workaround…

It’s like the engine couldn’t find the map at runtime or something like that. Something like a wrong folder path in the .ini files maybe.

So :

  • open the (broken) map
  • file/save current as … (a new map name in another folder)

Open the new map…
And everything is working fine.

EDIT : It might be because my maps was in a folder named “[Levels]” : maybe unreal hate brackets ] since 4.15.2…