When I want to log in to my database I got this error ..
I don't know where is the problem ..
It was completely functional ..

odoo.addons.base.ir.ir_qweb.qweb.QWebException
odoo.addons.base.ir.ir_qweb.qweb.QWebException: Name node can't be used with 'None' constant
Traceback (most recent call last):
  File "/home/nebil/Documents/odoo/odoo11/odoo/odoo/addons/base/ir/ir_qweb/qweb.py", line 331, in compile
    unsafe_eval(compile(astmod, '<template>', 'exec'), ns)
ValueError: Name node can't be used with 'None' constant

Error when compiling AST
ValueError: Name node can't be used with 'None' constant
Template: 162
Path: /templates/t/t/form/div[4]/button
Node: <button type="submit" class="btn btn-primary">Log in</button>