Merge pull request #2369 from Bacchusgift/master

修复了一个潜在可能的bug，当某条任务的executor_params为null时，会造成NPE

xxl-job-core/src/main/java/com/xxl/job/core/handler/impl/ScriptJobHandler.java

@@ -72,6 +72,10 @@ public class ScriptJobHandler extends IJobHandler {
 
         // script params：0=param、1=分片序号、2=分片总数
         String[] scriptParams = new String[3];
+        // 防止 XxlJobHelper.getJobParam() 为null，造成NPE
+        if (XxlJobHelper.getJobParam() == null) {
+            scriptParams[0] = "";
+        }
         scriptParams[0] = XxlJobHelper.getJobParam();
         scriptParams[1] = String.valueOf(XxlJobContext.getXxlJobContext().getShardIndex());
         scriptParams[2] = String.valueOf(XxlJobContext.getXxlJobContext().getShardTotal());