Fix For ONOS-5396:Causing NPE:for REST API- GET /applications/{name}

Change-Id: I652f4620a741f64bc71f2555ad801eb00e7c951f
diff --git a/web/api/src/main/java/org/onosproject/rest/resources/ApplicationsWebResource.java b/web/api/src/main/java/org/onosproject/rest/resources/ApplicationsWebResource.java
index 6163af4..df12dae 100644
--- a/web/api/src/main/java/org/onosproject/rest/resources/ApplicationsWebResource.java
+++ b/web/api/src/main/java/org/onosproject/rest/resources/ApplicationsWebResource.java
@@ -78,7 +78,7 @@
     @Path("{name}")
     public Response getApp(@PathParam("name") String name) {
         ApplicationAdminService service = get(ApplicationAdminService.class);
-        ApplicationId appId = service.getId(name);
+        ApplicationId appId = nullIsNotFound(service.getId(name), APP_NOT_FOUND);
         return response(service, appId);
     }