Description of problem:
It throw error of 'Can\'t call method "dm_contacts_as_email" on an undefined value when executing DependentProducts.get against products which contact user not set yet.

Version-Release number of selected component (if applicable):
5.0.3.rh6

How reproducible:
100%

Steps to Reproduce:
1.The product 'Bugzilla' doesn't set any contact for depend product in amdin
2.Execute xmlrpc method like:
proxy.DependentProducts.get({'names': ['Bugzilla'], 'Bugzilla_login': 'qgong', 'Bugzilla_password': '*******'})
3.

Actual results:
  File "/usr/lib64/python2.7/xmlrpclib.py", line 1240, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib64/python2.7/xmlrpclib.py", line 1599, in __request
    verbose=self.__verbose
  File "/usr/lib64/python2.7/xmlrpclib.py", line 1280, in request
    return self.single_request(host, handler, request_body, verbose)
  File "/usr/lib64/python2.7/xmlrpclib.py", line 1313, in single_request
    return self.parse_response(response)
  File "/usr/lib64/python2.7/xmlrpclib.py", line 1490, in parse_response
    return u.close()
  File "/usr/lib64/python2.7/xmlrpclib.py", line 799, in close
    raise Fault(**self._stack[0])
xmlrpclib.Fault: <Fault -32000: 'Can\'t call method "dm_contacts_as_email" on an undefined value at /loader/0x7f4732074e78/Bugzilla/Extension/DependentProducts/WebService/DependentProducts.pm line 223.\n'>


Expected results:
Just list out the data.

Additional info: