[github-252] wrong file name format for external links

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1893699 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFRelation.java b/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFRelation.java
index ee502b1..545b575 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFRelation.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFRelation.java
@@ -312,7 +312,7 @@
     public static final XSSFRelation EXTERNAL_LINKS = new XSSFRelation(
         "application/vnd.openxmlformats-officedocument.spreadsheetml.externalLink+xml",
         "http://schemas.openxmlformats.org/officeDocument/2006/relationships/externalLink",
-        "/xl/externalLinks/externalLink#.xmll",
+        "/xl/externalLinks/externalLink#.xml",
         ExternalLinksTable::new, ExternalLinksTable::new
     );