SLING-10425: fix an NPE in JSON conversion (#8)

diff --git a/src/main/java/org/apache/sling/servlets/get/impl/util/JsonObjectCreator.java b/src/main/java/org/apache/sling/servlets/get/impl/util/JsonObjectCreator.java
index 72dbb02..bdfaf02 100644
--- a/src/main/java/org/apache/sling/servlets/get/impl/util/JsonObjectCreator.java
+++ b/src/main/java/org/apache/sling/servlets/get/impl/util/JsonObjectCreator.java
@@ -242,7 +242,7 @@
         } catch (IOException ignore) {
         }
         if (index == -1) {
-            return valueMap.get(key, Long.class);
+            return valueMap.get(key, index);
         }
         final Long[] lengths = valueMap.get(key, Long[].class);
         if (lengths != null && lengths.length > index) {