GitHub Action assign an environment variable using a workflow_dispatch variable or job output

I have a GitHub Action workflow that can be triggered in two ways, via a pull_request and via a workflow dispatch.

During a pull_request, one of the steps generates an output that will be used in a later step.

During a workflow dispatch, the user manually inputs a custom output that will be used in a later step.

How do I use that output without running into null values? I can only use one of those outputs to assign to a variable, how can I make it accept both?

How about utilizing github.event_name context to conditionally set a variable that you can use in a later step? It requires an extra step, but is relatively straightforward.

my-workflow.yml:

name: Use input or job output

on:
  workflow_dispatch:
    inputs:
      my_input:
        description: Some workflow input
        type: string
  pull_request:
  
jobs:
  job1:
    runs-on: ubuntu-latest
    steps:
      - id: set_output
        run: echo "my_output=helloworld" >> $GITHUB_OUTPUT

      - name: Save job output OR workflow dispatch to Env
        run: |
          if [[ ${{ github.event_name == 'workflow_dispatch' }} == true ]]; then
            my_variable=${{ inputs.my_input }}
          else
            my_variable=${{ steps.set_output.outputs.my_output }}
          fi
          echo "my_variable=$my_variable" >> $GITHUB_ENV

      - name: Use the variable from previous step
        run: echo ${{ env.my_variable }}

If you run this manually from a workflow_dispatch, env.my_variable will be whatever string you input. If not (triggered by a pull request), env.my_variable will be my_output from the set_output step.