LogSoyData: Properly handle null revision in Next link

Change-Id: I70a03b6699078f320144bb7ada758c6ce5ecf8a2

java/com/google/gitiles/LogSoyData.java

diff --git a/java/com/google/gitiles/LogSoyData.java b/java/com/google/gitiles/LogSoyData.java
index 2f906fe..6a27782 100644
--- a/java/com/google/gitiles/LogSoyData.java
+++ b/java/com/google/gitiles/LogSoyData.java
@@ -178,8 +178,10 @@
     GitilesView.Builder copy = GitilesView.log().copyFrom(view);
     if (view.getRevision() != Revision.NULL) {
       copy.setRevision(view.getRevision());
-    } else {
+    } else if (revision != null) {
       copy.setRevision(Revision.named(revision));
+    } else {
+      copy.setRevision(Revision.NULL);
     }
     if (view.getOldRevision() != Revision.NULL) {
       copy.setOldRevision(view.getOldRevision());