I use the same code, but my ‘reference-path’ looks different:
Instead of:
static ConstructorHelpers::FObjectFinder<UClass> TreeFinder(TEXT(“Blueprint’/Game/Tree_BP.Tree_BP’”));
I use:
static ConstructorHelpers::FObjectFinder<UClass> TreeFinder(TEXT(“Class’/Game/Tree_BP.Tree_BP**_C**'”));
Note the suffix _C, I believe it’s necessary to reference the generated Blueprint-Class.
Hope that helps.