针对对象属性取值加了null值判断，防止出现空指针的异常出现

ureport2-core/src/main/java/com/bstek/ureport/Utils.java

@@ -159,6 +159,7 @@ public class Utils implements ApplicationContextAware{
 	}
 	
 	public static Object getProperty(Object obj,String property){
+		if(obj==null)return null;
 		try{
 			if(obj instanceof Map && property.indexOf(".")==-1){
 				Map<?,?> map=(Map<?,?>)obj;