fix(backend): Resolves issue when using task dependent on ParallelFor completion

[farridav]

Fix issue where tasks preceeding parallel for loops that recieve pipeline parameters, are wrongly expected to have task attributes

Description of your changes:
Im checking to see if the channel input actually has a task before trying to get its name, avoiding an AttributeError that i get otherwise

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[google-oss-prow]

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[google-oss-prow]

Hi @farridav. Thanks for your PR.

I'm waiting for a kubeflow member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[hbelmiro]

/ok-to-test

[github-actions]

Approvals successfully granted for pending runs.

[rimolive]

@farridav Before sending the PR, it would be good ensure that your contribution relies on the KFP code style. You can take a look at https://github.com/kubeflow/pipelines/blob/master/sdk/CONTRIBUTING.md#code-style for more reference.

In the failed test, you need to run this command to understand what you need to change:

yapf --diff sdk/python/kfp/compiler/compiler_utils.py

[hbelmiro]

/ok-to-test

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Approvals successfully granted for pending runs.

[hbelmiro]

/ok-to-test

[github-actions]

Approvals successfully granted for pending runs.