remember updated associations.

src/xvba_subpic.c

@@ -62,6 +62,7 @@ subpicture_add_association(
         return -1;
 
     assocs[obj_subpicture->assocs_count++] = assoc;
+    obj_subpicture->assocs = assocs;
     return 0;
 }
 

src/xvba_video.c

@@ -239,6 +239,7 @@ int surface_add_association(
         return -1;
 
     assocs[obj_surface->assocs_count++] = assoc;
+    obj_surface->assocs = assocs;
     return 0;
 }