bugfix: Selective增强插件，对于主键为字符串是没有if节点的，不需要进行isSelective()操作

src/main/java/com/itfsw/mybatis/generator/plugins/SelectiveEnhancedPlugin.java

@@ -232,6 +232,8 @@ public class SelectiveEnhancedPlugin extends BasePlugin {
         XmlElement whenEle = new XmlElement("when");
         whenEle.addAttribute(new Attribute("test", prefix + "isSelective()"));
         for (Element ele : element.getElements()) {
+            // 对于字符串主键，是没有if判断节点的
+            if (ele instanceof XmlElement){
                 // if的text节点
                 XmlElement xmlElement = (XmlElement) ele;
                 TextElement textElement = (TextElement) xmlElement.getElements().get(0);
@@ -263,6 +265,9 @@ public class SelectiveEnhancedPlugin extends BasePlugin {
                 ifEle.addAttribute(new Attribute("test", prefix + "isSelective(\'" + field + "\')"));
                 ifEle.addElement(textElement);
                 whenEle.addElement(ifEle);
+            } else {
+                whenEle.addElement(ele);
+            }
         }
 
         // otherwise