ValueError: Expected singleton: syd_bpm.activity()

[Rafaellinos]

"""
Odoo Server Error

Traceback (most recent call last):
File "/opt/odoo12/odoo/odoo/models.py", line 4741, in ensure_one
_id, = self._ids
ValueError: not enough values to unpack (expected 1, got 0)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/opt/odoo12/odoo/odoo/http.py", line 656, in _handle_exception
return super(JsonRequest, self)._handle_exception(exception)
File "/opt/odoo12/odoo/odoo/http.py", line 314, in _handle_exception
raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
File "/opt/odoo12/odoo/odoo/tools/pycompat.py", line 87, in reraise
raise value
File "/opt/odoo12/odoo/odoo/http.py", line 698, in dispatch
result = self._call_function(**self.params)
File "/opt/odoo12/odoo/odoo/http.py", line 346, in _call_function
return checked_call(self.db, *args, **kwargs)
File "/opt/odoo12/odoo/odoo/service/model.py", line 98, in wrapper
return f(dbname, *args, **kwargs)
File "/opt/odoo12/odoo/odoo/http.py", line 339, in checked_call
result = self.endpoint(*a, **kw)
File "/opt/odoo12/odoo/odoo/http.py", line 941, in call
return self.method(*args, **kw)
File "/opt/odoo12/odoo/odoo/http.py", line 519, in response_wrap
response = f(*args, **kw)
File "/opt/odoo12/odoo/addons/web/controllers/main.py", line 966, in call_button
action = self._call_kw(model, method, args, {})
File "/opt/odoo12/odoo/addons/web/controllers/main.py", line 954, in _call_kw
return call_kw(request.env[model], method, args, kwargs)
File "/opt/odoo12/odoo/odoo/api.py", line 759, in call_kw
return _call_kw_multi(method, model, args, kwargs)
File "/opt/odoo12/odoo/odoo/api.py", line 746, in _call_kw_multi
result = method(recs, *args, **kwargs)
File "/opt/odoo12/odoo/extra_addons/syd_process_maker/models/process.py", line 303, in update_processes
act.is_start_activity = True
File "/opt/odoo12/odoo/odoo/fields.py", line 1024, in set
record.ensure_one()
File "/opt/odoo12/odoo/odoo/models.py", line 4744, in ensure_one
raise ValueError("Expected singleton: %s" % self)
ValueError: Expected singleton: syd_bpm.activity()
"""
Using Odoo12 and Processmaker 3.3.4 CE.
On branch 12, when I try to update processes.

I solved by just checking if the search returns something:
"""

....
act = self.env['syd_bpm.activity'].search([('pm_activity_id', '=', activity['act_uid'])], limit=1)
if act:
    act.is_start_activity = True
    ....

"""
on syd_process_maker/models/process.py

I honestly didn't read all the code and don't know if that's the best solution, but it solved my problem. For some reason, this error doesn't happen on Odoo 13.