workflows: make sure field attributions are imported as strings (#42644)

tests/test_workflow_import.py

@@ -690,6 +690,21 @@ def test_set_backoffice_fields_action(pub):
     assert item2.fields == [{'field_id': 'bo1', 'value': '=form_var_foo'}]
 
 
+def test_set_backoffice_fields_action_boolean(pub):
+    wf = Workflow(name='status')
+    st1 = wf.add_status('Status1', 'st1')
+
+    item = SetBackofficeFieldsWorkflowStatusItem()
+    item.id = '_item'
+    item.fields = [{'field_id': 'bo1', 'value': 'True'}]
+    st1.items.append(item)
+    item.parent = st1
+
+    wf2 = assert_import_export_works(wf)
+    item2 = wf2.possible_status[0].items[0]
+    assert item2.fields == [{'field_id': 'bo1', 'value': 'True'}]
+
+
 def test_action_condition(pub):
     wf = Workflow(name='status')
     st1 = wf.add_status('Status1', 'st1')

wcs/wf/profile.py

@@ -89,8 +89,8 @@ class FieldNode(XmlSerialisable):
     node_name = 'field'
 
     def __init__(self, rule={}):
-        self.field_id = rule.get('field_id')
-        self.value = rule.get('value')
+        self.field_id = rule.get('field_id') or ''
+        self.value = rule.get('value') or ''
 
     def as_dict(self):
         return {