Reuse constant

src/main/java/org/apache/commons/codec/language/DaitchMokotoffSoundex.java

diff --git a/src/main/java/org/apache/commons/codec/language/DaitchMokotoffSoundex.java b/src/main/java/org/apache/commons/codec/language/DaitchMokotoffSoundex.java
index 881b78c..cbade2b 100644
--- a/src/main/java/org/apache/commons/codec/language/DaitchMokotoffSoundex.java
+++ b/src/main/java/org/apache/commons/codec/language/DaitchMokotoffSoundex.java
@@ -462,7 +462,7 @@
                     if (branching) {
                         nextBranches.clear();
                     }
-                    final String[] replacements = rule.getReplacements(inputContext, lastChar == '\0');
+                    final String[] replacements = rule.getReplacements(inputContext, lastChar == NUL);
                     final boolean branchingRequired = replacements.length > 1 && branching;
                     for (final Branch branch : currentBranches) {
                         for (final String nextReplacement : replacements) {