gobj: default current_thread arg for Geom.get_animated_vertex_data()

panda/src/gobj/geom.h

@@ -85,7 +85,7 @@ PUBLISHED:
   void offset_vertices(const GeomVertexData *data, int offset);
   int make_nonindexed(bool composite_only);
 
-  CPT(GeomVertexData) get_animated_vertex_data(bool force, Thread *current_thread) const;
+  CPT(GeomVertexData) get_animated_vertex_data(bool force, Thread *current_thread = Thread::get_current_thread()) const;
 
   INLINE bool is_empty() const;