[BUG] [JS Client]Number Format in Plurals usage doesn't follow region when getTranslation API's response is null from Singleton service.

Describe the bug
Number Format in Plurals usage doesn't follow region when getTranslation API's response is null from Singleton service.
The behavior is inconsistent with getTranslation API's response has corresponding translation.
e.g.
response has related translation:
fr/IT or fr-IT: translation displays as fr translation and number format is IT format.
response is null:
it/IT or it-IT: translation displays as local source and number format is EN format.

To Reproduce
Steps to reproduce the behavior:

1. Using get multiple component with combineRequest option is true.
2. Request one language/region or language that doesn't has corresponding translation in Singleton service. (e.g. it-IT or it/IT and there isn't it translation - messages_it.json in Singleton service.)
3. Request the translation and plurals and numbers patterns that mentioned in step 2.

Actual behavior
Since no it translation in Singleton service, the response from service is null. And the plurals behavior as below:
it/IT or it-IT: translation displays as local source and number format is EN format.

Expected behavior
The behavior should be consistent. Number format should follow provided region.