Check for null to handle the current thread's Context ClassLoader being null

git-svn-id: https://svn.apache.org/repos/asf/incubator/openjpa/trunk@489777 13f79535-47bb-0310-9956-ffa450edef68

openjpa-lib/src/main/java/org/apache/openjpa/lib/util/MultiClassLoader.java

@@ -215,6 +215,9 @@ public class MultiClassLoader extends ClassLoader {
             if (loader == THREAD_LOADER)
                 loader = Thread.currentThread().getContextClassLoader();
 
+            if (loader == null) // skip 
+                continue;
+
             rsrc = loader.getResource(name);
             if (rsrc != null)
                 return rsrc;