Use standard Ext JS ComboBox when field value is in set (work in all

cases).

modules/plugin_dbui/converter.py

@@ -95,10 +95,11 @@ def _to_field(field, linkedcombo=True, **kwargs):
                        valueField=encode_field(k_tablename, k_key),
                        store=get_store_id(k_tablename))
 
-    # set field
+    # set field. Use the basic Ext JS ComboBox
     elif is_set_field(field):
-        cfg = ComboBox(name=f_name,
-                       store=get_set_field(field))
+        cfg = dict(name=f_name,
+                   store=get_set_field(field),
+                   xtype='combobox')
         
     # other types of fields
     else: