gobj: fix static init ordering issue with VertexTransform cycler

This comes up when building with DEBUG_THREADS; there is a PipelineCycler created at static init time, and the type tracking in Pipeline won't work properly if the CData's parent's TypeHandle has not yet been initialized.

panda/src/gobj/vertexTransform.h

@@ -67,6 +67,7 @@ private:
     virtual int complete_pointers(TypedWritable **plist, BamReader *manager);
     virtual void fillin(DatagramIterator &scan, BamReader *manager);
     virtual TypeHandle get_parent_type() const {
+      VertexTransform::init_type();
       return VertexTransform::get_class_type();
     }