FilteredRepository: don't use deprecated getRef

Change-Id: I9d6a76a767edcc1ef22b1d9efbd2522b279f9682
diff --git a/src/main/java/com/googlesource/gerrit/plugins/gitiles/FilteredRepository.java b/src/main/java/com/googlesource/gerrit/plugins/gitiles/FilteredRepository.java
index 0550e6e..b7af9bf 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/gitiles/FilteredRepository.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/gitiles/FilteredRepository.java
@@ -142,7 +142,7 @@
 
   @Override
   public ReflogReader getReflogReader(String refName) throws IOException {
-    return getRef(refName) != null ? delegate.getReflogReader(refName) : null;
+    return exactRef(refName) != null ? delegate.getReflogReader(refName) : null;
   }
 
   @Override