Description of problem:
when enter new tag name in a case page, cannot show auto-complete list and server error happens. Following is the error raised in development env.

AttributeError at /management/tags/

'Objects' object has no attribute 'object'

Request Method: 	GET
Request URL: 	http://127.0.0.1:8000/management/tags/?name__startswith=abd&info_type=tags&format=ulli&field=name
Django Version: 	1.5.5
Exception Type: 	AttributeError
Exception Value: 	

'Objects' object has no attribute 'object'

Exception Location: 	./tcms/core/ajax.py in get, line 214
Python Executable: 	/home/chen/Virtualenvs/nitrate/bin/python
Python Version: 	2.7.5
Python Path: 	

['.',
 '.',
 '/home/chen/Virtualenvs/nitrate/bin',
 '/home/chen/Virtualenvs/nitrate/lib64/python27.zip',
 '/home/chen/Virtualenvs/nitrate/lib64/python2.7',
 '/home/chen/Virtualenvs/nitrate/lib64/python2.7/plat-linux2',
 '/home/chen/Virtualenvs/nitrate/lib64/python2.7/lib-tk',
 '/home/chen/Virtualenvs/nitrate/lib64/python2.7/lib-old',
 '/home/chen/Virtualenvs/nitrate/lib64/python2.7/lib-dynload',
 '/usr/lib64/python2.7',
 '/usr/lib/python2.7',
 '/usr/lib64/python2.7/lib-tk',
 '/home/chen/Virtualenvs/nitrate/lib/python2.7/site-packages',
 './tcms/core/lib']



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