Convert negative id value as None when set by the client

Domain inversion may force a unique value based on the default value from
PYSON evaluation. In such case it means that no record can be set.

Closes #12799
(grafted from 48463dae759ea1473b258ed905ba2c15fe96e10c)

--HG--
branch : 6.0

sao/src/model.js

@@ -2073,6 +2073,10 @@
                     rec_name = '';
                 }
             }
+            if ((value < 0) && (this.name != record.group.parent_name)) {
+                value = null;
+                rec_name = '';
+            }
             Sao.setdefault(
                 record._values, this.name + '.', {}).rec_name = rec_name;
             Sao.field.Many2One._super.set_client.call(this, record, value,

tryton/tryton/gui/window/view_form/model/field.py

@@ -490,6 +490,8 @@ class M2OField(Field):
                     self.name + '.', {}).get('rec_name', '')
             else:
                 rec_name = ''
+        if value and value < 0 and self.name != record.parent_name:
+            value, rec_name = None, ''
         record.value.setdefault(self.name + '.', {})['rec_name'] = rec_name
         super(M2OField, self).set_client(record, value,
             force_change=force_change)