"Accessed None to read property SplineRef"

Hi,
I get this error:
“Blueprint Runtime Error: “Accessed None trying to read property SplineRef”. Node: Set Total Spine Length Graph: Setup Spline Mesh Components Function: Setup Spline Mesh Components Blueprint: SplineMeshChild”
when loading into a new Level at runtime. I guess theres something wrong with my landscape because the file is in the Directory Engine/Landmass/Landscape/BlueprintBrushes. I dont understand why SplineRef is none in this case. Do you have any Idea what could fix it?

(post deleted by author)

Before using a Spline, check if it exists. To do this, you can use Is Valid—make sure to use Macros specifically.