Fix test finalization, if no chart was installed

Change-Id: I97672e90f25cc93704e8746defeaf54f93eb97a8
diff --git a/tests/helpers/helm.py b/tests/helpers/helm.py
index 73ac6fa..4222773 100644
--- a/tests/helpers/helm.py
+++ b/tests/helpers/helm.py
@@ -177,6 +177,6 @@
 
         charts = self.list(namespace)
         for chart in charts:
-            if chart["name"] in exceptions:
+            if exceptions and chart["name"] in exceptions:
                 continue
             self.delete(chart["name"], namespace)