Prevent potential null-pointer access

Path.getFilename can return null.  Protect against dereferencing
a null value.

Change-Id: Ibcda5ada4b8936b7e7520b840368ed0976ea1bb0
diff --git a/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/config/PluginProperties.java b/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/config/PluginProperties.java
index 5976245..36ba106 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/config/PluginProperties.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/config/PluginProperties.java
@@ -115,7 +115,10 @@
   @Override
   public String getName() {
     if (propertiesFile != null) {
-      return FilenameUtils.removeExtension(propertiesFile.getFileName().toString());
+      Path path = propertiesFile.getFileName();
+      if (path != null) {
+        return FilenameUtils.removeExtension(path.toString());
+      }
     }
     return null;
   }