Fix T88605: Alembic import crashes when missing arbGeomParams

Add check for the `arbGeomParams` property being valid, before attempting
to access a sub-property from it.

source/blender/io/alembic/intern/abc_customdata.cc

@@ -497,7 +497,7 @@ void read_generated_coordinates(const ICompoundProperty &prop,
                                 const CDStreamConfig &config,
                                 const Alembic::Abc::ISampleSelector &iss)
 {
-  if (prop.getPropertyHeader(propNameOriginalCoordinates) == nullptr) {
+  if (!prop.valid() || prop.getPropertyHeader(propNameOriginalCoordinates) == nullptr) {
     /* The ORCO property isn't there, so don't bother trying to process it. */
     return;
   }