#923 Add commands to run on unregister

src/main/java/fr/xephi/authme/settings/commandconfig/CommandMigrationService.java

@@ -30,13 +30,18 @@ class CommandMigrationService implements MigrationService {
         final CommandConfig commandConfig = CommandSettingsHolder.COMMANDS.getValue(resource);
         final boolean didMoveCommands = transformOldCommands(commandConfig);
 
-        if (didMoveCommands) { // TODO ConfigMe/#29: Check that loaded file isn't completely empty
+        if (didMoveCommands || isFileEmpty(resource)) {
             resource.setValue("", commandConfig);
             return true;
         }
         return false;
     }
 
+    private boolean isFileEmpty(PropertyResource resource) {
+        Object root = resource.getObject("");
+        return (root instanceof Map) && ((Map) root).isEmpty();
+    }
+
     /**
      * Adds command settings from their old location (in config.yml) to the given command configuration object.
      *