Services with invalid themes hang the UI when you attempt to add them

For a given service if the theme.json file is not properly formatted, Ambari server will still start 'successfully' but attempts to add that service to the cluster will fail.

The Ambari server start will log the theme error. Although it neglects to mention which theme file and service are in error.

When you attempt to add the service, it will query for the service's themes:

api/v1/stacks/<stack>/versions/<version>/services?StackServices/service_name.in(HDFS,YARN,MAPREDUCE2,ZOOKEEPER,RANGER,RANGER_KMS,SLIDER)&themes/ThemeInfo/default=true&fields=themes/*

This will return something like the following for the invalid theme:

"ThemeInfo" :

{ "default" : true, "file_name" : "theme_version_2.json", "service_name" : "RANGER_KMS", "stack_name" : "BigInsights", "stack_version" : "4.3", "theme_data" : null }

where the theme_data is null.