Unified Push responds with 404 if no installations exist for a variant

Before 0.11.0, if a wrong (non-existent) variant ID was used, user got 404 Not Found, and when an existing variant ID was used, user got a response with an empty json array. That way user could easily say if the variant id was wrong or not. Now, user gets 404 even when the variant ID is correct, but the variant has no installations. The old code: [1] and the new code: [2]

1 - https://github.com/aerogear/aerogear-unifiedpush-server/blob/2ecf73ea4e3bf4d82705222a219a62f7c8af04bb/jaxrs/src/main/java/org/jboss/aerogear/unifiedpush/rest/registry/applications/InstallationManagementEndpoint.java#L56-L60
2 - https://github.com/aerogear/aerogear-unifiedpush-server/blob/master/jaxrs/src/main/java/org/jboss/aerogear/unifiedpush/rest/registry/applications/InstallationManagementEndpoint.java#L62-L64