FIX: issue when DataSource request is empty

If client requested empty string in DataSource endpoint ClassMethod GetDataSource() return status 200

Author: Frisle

MDX2JSON/Utils.cls

@@ -291,7 +291,7 @@ ClassMethod GetDataSource(pDataSource As %String)
 	set st = $$$OK
 	try {
 
-		if ($FIND(pDataSource, ".pivot") = ($LENGTH(pDataSource) + 1)) {
+		if ($FIND(pDataSource, ".pivot") = ($LENGTH(pDataSource) + 1) && pDataSource '="") {
 			set st = ..OpenPivotByName(pDataSource, .dataSource)
 			return:($$$ISERR(st)) st