YMS migration to onos-yangtool 1.10

Change-Id: I22ddf23f813840e0afec1e7713a86891f2a52f28
diff --git a/apps/yms/app/src/main/java/org/onosproject/yms/app/ych/defaultcodecs/xml/XmlCodecSingleInstanceLeafHandler.java b/apps/yms/app/src/main/java/org/onosproject/yms/app/ych/defaultcodecs/xml/XmlCodecSingleInstanceLeafHandler.java
index f44f9b2..e7b786e 100644
--- a/apps/yms/app/src/main/java/org/onosproject/yms/app/ych/defaultcodecs/xml/XmlCodecSingleInstanceLeafHandler.java
+++ b/apps/yms/app/src/main/java/org/onosproject/yms/app/ych/defaultcodecs/xml/XmlCodecSingleInstanceLeafHandler.java
@@ -29,6 +29,9 @@
     @Override
     public void setXmlValue(YdtContext ydtContext,
                             Stack<Element> elementStack) {
-        elementStack.peek().setText(ydtContext.getValue());
+
+        if (ydtContext.getValue() != null) {
+            elementStack.peek().setText(ydtContext.getValue());
+        }
     }
 }