Fall back to loading only base config if no site configs are found

The plugin was only loading the base config if at least one site
config was present, even if that site config was just an empty file.

When no site configs are found, just load the base config.

Change-Id: I217d647923f3ca7f81ed1bd03b97556b0088515f
diff --git a/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/Manager.java b/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/Manager.java
index 84d47cb..99804d4 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/Manager.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/Manager.java
@@ -117,7 +117,7 @@
     Properties base = propFactory.create(pluginDataDir.resolve(pluginName + FILE_EXT));
     base.load();
 
-    // Load site
+    // Load sites
     try (DirectoryStream<Path> ds = Files.newDirectoryStream(pluginDataDir.resolve(SITE_DIR), "*" + FILE_EXT)) {
       for (Path configFile : ds) {
         Properties site = propFactory.create(configFile);
@@ -128,6 +128,10 @@
     } catch (IOException iex) {
       LOGGER.warn(iex.getMessage());
     }
+    if (propList.isEmpty()) {
+      LOGGER.warn("No site configs found. Using base config only!");
+      propList.add(base);
+    }
     return propList;
   }
 }