Unable to uninstall Module - Openerp

[shadyds]

when I'm going to uninstall my own module.its gives a error. (OpenErp ver 7)in my class i entered different different modification also.but not i clear all that stuffs and keep below codes only.please help me to find what is the issue with this..now when i try to install address_book module also occured this error\[code\] File "/home/priyan/Software/openerp-7.0-20130309-002120/openerp/modules/registry.py", line 218, in new openerp.modules.load_modules(registry.db, force_demo, status, update_module) File "/home/priyan/Software/openerp-7.0-20130309-002120/openerp/modules/loading.py", line 416, in load_modules pool.get('ir.module.module').module_uninstall(cr, SUPERUSER_ID, mod_ids_to_remove) File "/home/priyan/Software/openerp-7.0-20130309-002120/openerp/addons/base/module/module.py", line 439, in module_uninstall ir_model_constraint._module_data_uninstall(cr, uid, constraint_ids, context) File "/home/priyan/Software/openerp-7.0-20130309-002120/openerp/addons/base/ir/ir_model.py", line 533, in _module_data_uninstall WHERE cs.contype=%s and cs.conname=%s and cl.relname=%s""", ('f', name, model_obj._table))AttributeError: 'NoneType' object has no attribute '_table'\[/code\]here is my view.xml file\[code\]<?xml version="1.0"?><openerp> <data> <!-- 1st part of the sim_view start --> <record model="ir.ui.view" id="worker_form"> <field name="name">Basic Data</field> <field name="model">checkroll.plucker</field> <field name="type">form</field> <field name="arch" type="xml"> <form string="Worker_test"> <field name="reg_no" /> <field name="worker_name" /> <field name="spouse_name" /> <field name="gender" /> <field name="epf_no" /> </form> </field> </record> <!--2nd part of the sim_view start --> <record model="ir.ui.view" id="worker_tree"> <field name="name">Basic Data</field> <field name="model">checkroll.plucker</field> <field name="type">tree</field> <field name="arch" type="xml"> <tree string="Worker_test"><!-- which columns need to shows in OpenERP List View --> <field name="reg_no" /> <field name="worker_name" /> <field name="spouse_name" /> </tree> </field> </record> <!-- 3rd part of the sim_view start --> <record model="ir.actions.act_window" id="action_worker_reg"> <field name="name">Worker Registration</field><!-- This shows what should screen caption in form/tree views --> <field name="res_model">checkroll.plucker</field> <field name="view_type">form</field> <field name="view_mode">tree,form</field> </record> </data></openerp>\[/code\]here is my class file\[code\]from openerp.osv import fields, osvimport randomclass checkroll(osv.osv): _name = "checkroll.plucker" _description = "This table is for keeping personal data of plucker" _columns = { 'reg_no': fields.char('Registration Number', size=256, required=True), 'worker_name': fields.char('Worker Name', size=256, required=True), 'spouse_name': fields.char('Spouse Name', size=256), 'gender' : fields.selection((('male', 'Male'), ('female', 'Female'), ('middle', 'Test')), 'Gender', required=True), 'epf_no':fields.char('EPF Number', size=256) }checkroll()\[/code\]