fields: fix MapMarkerSelectionWidget set_value method (#73617)

tests/form_pages/test_all.py

@@ -9513,6 +9513,12 @@ def test_form_item_map_data_source(pub, http_requests):
         'err_class': 'Invalid request',
     }
 
+    formdef.fields = [
+        fields.ItemField(id='1', label='map', display_mode='map', prefill={'type': 'string', 'value': '1;2'}),
+    ]
+    formdef.store()
+    app.get('/test/', status=200)  # no error
+
 
 def test_form_item_dynamic_map_data_source(pub, http_requests):
     NamedDataSource.wipe()

wcs/qommon/form.py

@@ -3310,6 +3310,9 @@ class MapMarkerSelectionWidget(MapWidget):
         CompositeWidget._parse(self, request)
         self.value = self.get('marker_id')
 
+    def set_value(self, value):
+        CompositeWidget.set_value(self, value)
+
 
 class HiddenErrorWidget(HiddenWidget):
     def set_error(self, error):