Don't die on empty values.

PR: 18625


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@274424 13f79535-47bb-0310-9956-ffa450edef68

WHATSNEW

@@ -90,6 +90,9 @@ Fixed bugs:
 * <tar> and <zip> didn't honor the defaultexcludes attribute for the
   implicit fileset.  Bugzilla Report 18637.
 
+* The <replacetokens> filter would throw an exception if the token's
+  value was an empty string.  Bugzilla Report 18625.
+
 Other changes:
 --------------
 * Shipped XML parser is now Xerces 2.4.0

src/main/org/apache/tools/ant/filters/ReplaceTokens.java

@@ -190,8 +190,10 @@ public final class ReplaceTokens
                 
                 final String replaceWith = (String) hash.get(key.toString());
                 if (replaceWith != null) {
-                    replaceData = replaceWith;
-                    replaceIndex = 0;
+                    if (replaceWith.length() > 0) {
+                        replaceData = replaceWith;
+                        replaceIndex = 0;
+                    }
                     return read();
                 } else {
                     String newData = key.toString() + endToken;