GraphQL: Fix empty successful pipeline analytics

What does this MR do and why?

This MR fixes a bug introduced in !157293 (merged), due to an optimization of node selection which wasn't taking into account the existing fields.

Changelog: fixed

Fixes #480090 (closed)

MR acceptance checklist

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Screenshots or screen recordings

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Go to the shell in your GDK gitlab directory and run bundle exec rake "gitlab:seed:runner_fleet". This will seed your GDK with some runners and jobs required for testing this MR.

2. Execute the following query at http://gdk.test:3000/-/graphql-explorer:

   {
     project(fullPath: "rf-top-level-group-1/rf-group-1.1/rf-group-1.1.1/rf-project-1-1-1-1") {
       pipelineAnalytics {
         weekPipelinesTotals
         weekPipelinesLabels
         weekPipelinesSuccessful
       }
     }
   }