check if key is present

drip-api/src/main/java/nl/uva/sne/drip/api/service/DeployService.java

@@ -468,6 +468,7 @@ public class DeployService {
                     jo.put("result", result);
                 }
             }
+            if (result.has("invocation")) {
                 JSONObject invocation = ((JSONObject) (result).get("invocation"));
                 if (invocation.has("module_args")) {
                     JSONObject module_args = (JSONObject) invocation.get("module_args");
@@ -493,7 +494,7 @@ public class DeployService {
                         invocation.put("msg", msg);
                         result.put("invocation", invocation);
                     }
-
+                }
             }
 
             newJa.put(jo);