FBX export: skip special properties when exporting custom properties

'_RNA_UI' (and rna runtime properties) should not be included, these
would have been included as string properties causing errors on reimport

backport rBAe4f4053de64e (fix for T59202) from 2.8 branch

Differential Revision: https://developer.blender.org/D4068

1 files changed, 11 insertions, 1 deletions

diff --git a/io_scene_fbx/export_fbx_bin.py b/io_scene_fbx/export_fbx_bin.py
index e82ceadd..ed1109e7 100644
--- a/io_scene_fbx/export_fbx_bin.py
+++ b/io_scene_fbx/export_fbx_bin.py
@@ -533,7 +533,17 @@ def fbx_data_element_custom_properties(props, bid):
     """
     Store custom properties of blender ID bid (any mapping-like object, in fact) into FBX properties props.
     """
-    for k, v in bid.items():
+    items = bid.items()
+
+    if not items:
+        return
+
+    rna_properties = {prop.identifier for prop in bid.bl_rna.properties if prop.is_runtime}
+
+    for k, v in items:
+        if k == '_RNA_UI' or k in rna_properties:
+            continue
+
         list_val = getattr(v, "to_list", lambda: None)()
 
         if isinstance(v, str):