Extend readonly condition on buttons of state changes

This commit refs #28612

stock.py

@@ -3,7 +3,7 @@
 from functools import wraps
 from trytond.pool import PoolMeta, Pool
 from trytond.model import fields, Workflow
-from trytond.pyson import Bool
+from trytond.pyson import Bool, Eval, Or
 from trytond.exceptions import UserError
 from trytond.i18n import gettext
 from trytond.transaction import Transaction
@@ -53,6 +53,16 @@ class Move(metaclass=PoolMeta):
             'readonly': Bool(True)
         })
 
+    @classmethod
+    def __setup__(cls):
+        super().__setup__()
+        for button in ['draft', 'cancel', 'assign', 'do']:
+            if cls._buttons[button].get('readonly'):
+                cls._buttons[button]['readonly'] |= Bool(Eval('unit_load'))
+            else:
+                cls._buttons[button]['readonly'] = Bool(Eval('unit_load'))
+            cls._buttons[button]['depends'].append('unit_load')
+
     @classmethod
     def validate(cls, records):
         super(Move, cls).validate(records)