fix some JSR 305 annotations

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1785617 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/sling/models/validation/impl/ModelValidationImpl.java b/src/main/java/org/apache/sling/models/validation/impl/ModelValidationImpl.java
index ce4d230..c7a2784 100644
--- a/src/main/java/org/apache/sling/models/validation/impl/ModelValidationImpl.java
+++ b/src/main/java/org/apache/sling/models/validation/impl/ModelValidationImpl.java
@@ -16,6 +16,8 @@
  */
 package org.apache.sling.models.validation.impl;
 
+import javax.annotation.Nonnull;
+
 import org.apache.sling.api.SlingHttpServletRequest;
 import org.apache.sling.api.resource.Resource;
 import org.apache.sling.models.factory.InvalidModelException;
@@ -82,7 +84,7 @@
         }
     }
     
-    private RuntimeException validate(Resource resource, boolean required) {
+    private RuntimeException validate(@Nonnull Resource resource, boolean required) {
         try {
             ValidationModel validationModel = validation.getValidationModel(resource, true);
             if (validationModel == null) {