make it not return http 400 when passing and empty source argument (#12259)

* make it not return http 400 when passing and empty source argument

* create a spec for the empty source hash bug

* compact checks for nil, empty? parameters

* use nil.blank? instead checking for nil

app/controllers/api/v1/accounts/credentials_controller.rb

@@ -25,7 +25,7 @@ class Api::V1::Accounts::CredentialsController < Api::BaseController
   end
 
   def user_settings_params
-    return nil unless params.key?(:source)
+    return nil if params[:source].blank?
 
     source_params = params.require(:source)