The name 'action' is referenced before it is defined in xenapi_conn.py

The code in the wait_for_task() method of xenapi_conn.py tries to set the 'error' key in the 'action' dict if an error is encountered. But that name is only defined if an 'id' was passed in to the method initially; in cases where no id was passed, the following traceback is returned:

Traceback (most recent call last):
  File "/home/ed/openstack/xen-host-config/nova/utils.py", line 467, in _inner
    self.f(*self.args, **self.kw)
  File "/home/ed/openstack/xen-host-config/nova/virt/xenapi_conn.py", line 416, in _poll_task
    action["error"] = str(error_info)
UnboundLocalError: local variable 'action' referenced before assignment