Adapt to changes in Gerrit API

IdentifiedUser#getByUserName now returns Optional<String> insteadof
a nullable String.

Change-Id: Ib41be4e4a09c1ea0db1ff74fd6e00cbee563ff91
Signed-off-by: Edwin Kempin <ekempin@google.com>
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java
index 90172f3..1971491 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java
@@ -95,8 +95,8 @@
   Action() {}
 
   private String getUserName() {
-    if (userProvider != null && userProvider.get().getUserName() != null) {
-      return userProvider.get().getUserName();
+    if (userProvider != null && userProvider.get().getUserName().isPresent()) {
+      return userProvider.get().getUserName().get();
     }
     return "?";
   }