Concrete composite

trying to make a concrete composite. whenever i tried to apply compressive load from wall, i get this error “Unable to convert parameter type from Null Pointer to Wall Pointer.
While executing line 13 columns 26 to 34 of source
While executing line 238 columns 10 to 20 of source GUI Console.
While processing line 238 of source GUI Console.
While executing line 230 columns 5 to 12 of source GUI Console.
While executing line 256 columns 2 to 6 of source GUI Console.
While processing line 256 of source GUI Console.”
i would really appreciate if anyone encounter same kind of error?

Hello @123,
This is most likely due to a FISH function that requires as an argument a wall pointer and you are supply a pointer that is null.