Fix: Blender Asset data is not JSONable, so skip it in export.

i_o.py

@@ -72,7 +72,8 @@ def export_to_json(trees, path="", write_file=True, only_selected=False):
                     "__annotations__", "original", "rna_type", "view_center",
                     "links", "nodes", "internal_links", "inputs", "outputs",
                     "__slots__", "dimensions", "type", "interface",
-                    "library_weak_reference", "parsed_tree", "node_tree_updater" ]
+                    "library_weak_reference", "parsed_tree", "node_tree_updater",
+                    "asset_data", "preview", ] # blender asset stuff
     # don't ignore: "bl_idname", "bl_label",
     # ignore the name, it's the dict - key for the node props
      # no that's stupid don't ignore the name good grief