Also remove ci_builds.artifacts_size when erased

app/models/ci/build.rb

@@ -340,6 +340,7 @@ module Ci
     def erase_artifacts!
       remove_artifacts_file!
       remove_artifacts_metadata!
+      self.artifacts_size = nil
       save
     end
 

spec/requests/ci/api/builds_spec.rb

@@ -482,6 +482,7 @@ describe Ci::API::API do
           expect(response).to have_http_status(200)
           expect(build.artifacts_file.exists?).to be_falsy
           expect(build.artifacts_metadata.exists?).to be_falsy
+          expect(build.artifacts_size).to be_falsy
         end
       end