Fix branchRedirect

java/com/google/gitiles/GitilesFilter.java

diff --git a/java/com/google/gitiles/GitilesFilter.java b/java/com/google/gitiles/GitilesFilter.java
index 41c6ea4..d4c310f 100644
--- a/java/com/google/gitiles/GitilesFilter.java
+++ b/java/com/google/gitiles/GitilesFilter.java
@@ -313,6 +313,7 @@
     setDefaultTimeCache();
     setDefaultBlameCache();
     setDefaultGitwebRedirect();
+    setDefaultBranchRedirect();
     setDefaultErrorHandler();
   }
 
@@ -420,6 +421,12 @@
     }
   }
 
+  private void setDefaultBranchRedirect() {
+    if (branchRedirect == null) {
+      branchRedirect = BranchRedirect.EMPTY;
+    }
+  }
+
   private void setDefaultErrorHandler() {
     if (errorHandler == null) {
       errorHandler = new DefaultErrorHandlingFilter(renderer);