title: Failing multiple field validation in SmartGWT
body: <p>I am trying to have a form field contain one or more elements that are defined in a different data source. Elements have a numeric id and a human-readable name. It all works well until I try to save; in this case, I always get the "Not a valid option" error.</p>
  
  <p>The form I am editing is based on a Campaigns datasource, that may be linked to zero or more Trunks.</p>
  
  <p>Datasource Trunks are defined as:</p>
  
  <pre><code>    DataSourceField fId = new DataSourceField(
              "trunkId", FieldType.INTEGER, "Id");
      fId.setPrimaryKey(Boolean.TRUE);
      fId.setHidden(Boolean.TRUE);
      fId.setCanEdit(Boolean.FALSE);
  
      DataSourceField fName = new DataSourceField(
              "trunkName", FieldType.TEXT, "Name");
      fName.setRequired(Boolean.TRUE);
  </code></pre>
  
  <p>Datasource Campaigns have a field "trunk" defined as:</p>
  
  <pre><code>    DataSourceField fTrunk  = new DataSourceField(
              "trunk",
              FieldType.INTENUM,
              "Trunk"
      );
      fTrunk.setMultiple(Boolean.TRUE);
      fTrunk.setForeignKey("CfgTrunkDS.trunkId");
  </code></pre>
  
  <p>And here is the form definition to allow for multiple values being selected:</p>
  
  <pre><code>    final DynamicForm form = new DynamicForm();
      form.setIsGroup(true);
      form.setGroupTitle("Update Campaign");
      form.setNumCols(4);
  
      form.setDataSource(dsCampaign);
      form.setUseAllDataSourceFields(Boolean.TRUE);
  
      final SelectItem selectItemMultipleGrid = new SelectItem("trunk");
      selectItemMultipleGrid.setTitle("Trunk to use");
      selectItemMultipleGrid.setMultiple(true);
      selectItemMultipleGrid.setMultipleAppearance(MultipleAppearance.PICKLIST);
      selectItemMultipleGrid.setOptionDataSource(CfgTrunkDS.getInstance());
      selectItemMultipleGrid.setValueField("trunkId");
      selectItemMultipleGrid.setDisplayField("trunkName");
  
  
      form.setFields(selectItemMultipleGrid);
  </code></pre>
  
  <p>I also see the multiple values correctly and if I look at the "trunk" fiels, I see a string like "12, 16" when I select elements whose ids are 12 and 16. But still does not pass validation. I also noticed that if I comment the OptionDataSource in the form definition, it works just as fine.</p>
  
  <p>What did I do wrong?</p>