Catch null reference in case no vc cache is defined

Change-Id: I6dda338e03e46030f2b6d2741cef73d9e1bbf71d
diff --git a/src/test/resources/krill.properties b/src/test/resources/krill.properties
index a6302b6..ea60670 100644
--- a/src/test/resources/krill.properties
+++ b/src/test/resources/krill.properties
@@ -1,4 +1,5 @@
 krill.version = ${project.version}
 krill.name = ${project.name}
 krill.indexDir = test-output
-krill.namedVC = vc
\ No newline at end of file
+krill.namedVC = vc
+krill.index.commit.count = 15
\ No newline at end of file