NO-JIRA: Fix NPE in conversion tests
diff --git a/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/dependency_resolution/ClasspathQuery.java b/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/dependency_resolution/ClasspathQuery.java
index 921d214..8b62a99 100644
--- a/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/dependency_resolution/ClasspathQuery.java
+++ b/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/dependency_resolution/ClasspathQuery.java
@@ -153,7 +153,12 @@
 
     private String buildClassPath(final Class<?> clientClazz, final Collection<String> gavs)
     {
-        List<File> classpathElements = new ArrayList<>(_classpathCache.getUnchecked(gavs));
+        final List<File> classpathElements = new ArrayList<>();
+        final List<File> cached = _classpathCache.getUnchecked(gavs);
+        if (cached != null)
+        {
+            classpathElements.addAll(cached);
+        }
         classpathElements.add(getLocalClasspathElement(clientClazz));
 
         final String collect = classpathElements.stream()