[CDM bug] Fix CDM crash when there's no CDM service

Move the service connector empty check before adding it to the service
connectors map. So when there's no CDM services, there won't be a value in the map.

Bug: 219784113

Test: manually tested no services case using CDM test app. The app
doesn't crash now.

Change-Id: Ib236d42a43c001c0ea5fa4debf5f832daee811c4
1 file changed