Fix binary file diff for anonymous users

Restore Gerrit.isSignedIn() check that was erroneously removed in
I7ec4a0beb.

Change-Id: Idbfd873e555c682b79e61ab220d6b57db9039e2e
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchTable.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchTable.java
index 218a6c3..178a583 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchTable.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchTable.java
@@ -261,8 +261,9 @@
 
   private static boolean isUnifiedPatchLink(final Patch patch) {
     return (patch.getPatchType().equals(PatchType.BINARY)
-        || Gerrit.getUserAccount().getGeneralPreferences().getDiffView()
-        .equals(DiffView.UNIFIED_DIFF));
+        || (Gerrit.isSignedIn()
+            && Gerrit.getUserAccount().getGeneralPreferences().getDiffView()
+            .equals(DiffView.UNIFIED_DIFF)));
   }
 
   private static String getFileNameOnly(Patch patch) {