Adapt to "Treat empty username as non-existing username"

IdentifiedUser#getUserName() no longer returns empty user names, hence
checking for null is sufficient.

Change-Id: I86256b9c9070e92c033ba328ae295e844d7a32b0
Signed-off-by: Edwin Kempin <ekempin@google.com>

src/main/java/com/googlesource/gerrit/plugins/download/scheme/SshScheme.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/download/scheme/SshScheme.java b/src/main/java/com/googlesource/gerrit/plugins/download/scheme/SshScheme.java
index ac198fb..9be9168 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/download/scheme/SshScheme.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/download/scheme/SshScheme.java
@@ -16,7 +16,6 @@
 
 import static com.google.gerrit.reviewdb.client.CoreDownloadSchemes.SSH;
 
-import com.google.common.base.Strings;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.extensions.config.DownloadScheme;
 import com.google.gerrit.server.CurrentUser;
@@ -85,7 +84,7 @@
       return null;
     }
     String username = userProvider.get().getUserName();
-    if (Strings.isNullOrEmpty(username)) {
+    if (username == null) {
       return null;
     }