增加：LC_SINGLE模型engine

smtweb-framework/bpm/src/main/java/cc/smtweb/system/bpm/web/design/form/ModelFormHelper.java

@@ -211,7 +211,7 @@ public class ModelFormHelper {
     public static String buildReqModel(ModelForm form) {
         PageDatasets datasets = form.getDatasets();
         PageModel pageInfo = parsePageInfo(form.getContent());
-        if (pageInfo == null) return "";
+        if (pageInfo == null || pageInfo.model == null) return "";
         for (Map<String, Object> model : pageInfo.model) {
             String db = (String) model.get("dataset");
             //没有配置db，配置有误，不处理