Ansible launcher: handle JJB with no macros

Handle the case where there are no 'builder' macros defined.

Change-Id: I5e4db4834df89ce1629000f116245c063ad96a3f
diff --git a/zuul/launcher/ansiblelaunchserver.py b/zuul/launcher/ansiblelaunchserver.py
index 232bd0c..8061176 100644
--- a/zuul/launcher/ansiblelaunchserver.py
+++ b/zuul/launcher/ansiblelaunchserver.py
@@ -939,7 +939,7 @@
             name = component
             component_data = {}
 
-        new_component = self.parser.data[component_type].get(name)
+        new_component = self.parser.data.get(component_type, {}).get(name)
         if new_component:
             for new_sub_component in new_component[component_list_type]:
                 new_components.extend(