Check for zero length before sending a characters event.  This fixes
minor regression with string115, etc. where tags were not being
collapsed if empty.

diff --git a/src/org/apache/xalan/serialize/SerializerToXML.java b/src/org/apache/xalan/serialize/SerializerToXML.java
index 9bd4566..148586b 100644
--- a/src/org/apache/xalan/serialize/SerializerToXML.java
+++ b/src/org/apache/xalan/serialize/SerializerToXML.java
@@ -1505,6 +1505,8 @@
   public void characters(char chars[], int start, int length)
           throws org.xml.sax.SAXException
   {
+    if(0 == length)
+      return;
 
     //    if (m_inEntityRef)
     //      return;