fix bug

pkg/ruleEngine/nodes/script_filter_node.go

@@ -11,12 +11,18 @@ import (
 )
 
 const jsWrapperPrifixTemplate = `function %s(msgStr, metaDataStr, msgType) { 
-									var msg = JSON.parse(msgStr);
-									var metaData = JSON.parse(metaDataStr);
-									if(!metaData === undefined)
-										metaData = {}
-									return %s(msg, metaData, msgType);
-									function %s(%s, %s, %s) {`
+if(!metaData === undefined)
+      metaData = {}   
+if(!msgStr === undefined)
+      metaData = {}
+if(!metaDataStr === undefined)
+      metaData = {}
+var msg = JSON.parse(msgStr);
+   var metaData = JSON.parse(metaDataStr);
+   if(!metaData === undefined)
+      metaData = {}
+   return %s(msg, metaData, msgType);
+   function %s(%s, %s, %s) {`
 const jsWrapperSuffix = `}}`
 const ruleNodeFuncName = "ruleNodeFunc"