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

spec/controllers/api/v1/accounts/credentials_controller_spec.rb

@@ -59,6 +59,19 @@ describe Api::V1::Accounts::CredentialsController do
         end
       end
 
+      describe 'with empty source list' do
+        before do
+          patch :update, params: {
+            display_name: "I'm a cat",
+            source: {},
+          }, as: :json
+        end
+
+        it 'returns http success' do
+          expect(response).to have_http_status(200)
+        end
+     end
+
       describe 'with invalid data' do
         before do
           patch :update, params: { note: 'This is too long. ' * 30 }