VisibleRefFilter: Fix NPE on check of edit ref when currAccountId is null

Let RefNames#isRefsEditOf(String, Account.Id) return false if the
account ID is null.

Change-Id: Ibfabac411261fab74deee989d87c69f00778b69a
Signed-off-by: Edwin Kempin <ekempin@google.com>

gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/RefNames.java

diff --git a/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/RefNames.java b/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/RefNames.java
index 1af82da..7c460de 100644
--- a/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/RefNames.java
+++ b/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/RefNames.java
@@ -177,6 +177,9 @@
   }
 
   public static boolean isRefsEditOf(String ref, Account.Id accountId) {
+    if (accountId == null) {
+      return false;
+    }
     String prefix = new StringBuilder(refsUsers(accountId))
         .append('/')
         .append(EDIT_PREFIX)