If a view was created with the DEFINER security and later the definer user
was dropped then a SELECT from the view throws the error message saying that
there is no definer user is registered. This is ok for a root but too much
for a mere user.

Now the st_table_list::prepare_view_securety_context() function reveals
the absence of the definer only to a superuser and throws the 'access denied'
error to others.