title: TypeError: object of type 'bool' has no len()
body: <p>I open a form view with many2many field and appear this error:</p>
  
  <pre><code>  File "/home/ingeos/coas/server/openerp/osv/osv.py", line 199, in execute
      res = self.execute_cr(cr, uid, obj, method, *args, **kw)
    File "/home/ingeos/coas/server/openerp/osv/osv.py", line 187, in 
     execute_cr
     return getattr(object, method)(cr, uid, *args, **kw)
    File "/home/ingeos/coas/server/openerp/osv/orm.py", line 3623, in read
     result = self._read_flat(cr, user, select, fields, context, load)
    File "/home/ingeos/coas/server/openerp/osv/orm.py", line 3744, in 
       _read_flat
     res2 = self._columns[f].get(cr, self, ids, f, user, context=context, 
    values=res)
    File 
    "/home/ingeos/coas/server/openerp/addons/one2many_sorted/__init__.py", line 113, in get
       o = getattr(o, m)
     File "/home/ingeos/coas/server/openerp/osv/orm.py", line 497, in 
  __getattr__
    return self[name]
  File "/home/ingeos/coas/server/openerp/osv/orm.py", line 468, in __getitem__
    elif field_column._type in ('one2many', 'many2many') and 
    len(result_line[field_name]):
  TypeError: object of type 'bool' has no len()
  </code></pre>
  
  <p>Can you tell me what is the problem?</p>