[java-atk-wrapper] Restore check against null parent

[Samuel Thibault <sthibaul src gnome org>]

commit 91c7b9ec4130923de530b185a9c5844891eba2ec
Author: Samuel Thibault <samuel thibault ens-lyon org>
Date:   Mon Jun 17 22:14:43 2019 +0200

    Restore check against null parent

 jni/src/jawobject.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)
---
diff --git a/jni/src/jawobject.c b/jni/src/jawobject.c
index 02dbe7e..fad4176 100644
--- a/jni/src/jawobject.c
+++ b/jni/src/jawobject.c
@@ -212,9 +212,13 @@ jaw_object_get_parent(AtkObject *atk_obj)
   jobject jparent = (*jniEnv)->CallStaticObjectMethod (jniEnv, atkObject, jmid, ac);
   (*jniEnv)->DeleteGlobalRef (jniEnv, ac);
 
-  AtkObject *parent_obj = (AtkObject*) jaw_object_table_lookup (jniEnv, jparent);
-  if (parent_obj != NULL )
-    return parent_obj;
+  if (jparent != NULL)
+  {
+    AtkObject *parent_obj = (AtkObject*) jaw_object_table_lookup (jniEnv, jparent);
+
+    if (parent_obj != NULL )
+      return parent_obj;
+  }
 
   // FIXME: Should we rather return null?
   return ATK_OBJECT(atk_get_root());