return nil instead of op, which is an interface containing nil

[megan07]

Fixes hashicorp/terraform-provider-google#5114

The issue here seems to be that op is an interface containing nil rather than nil. So, when checking if op == nil further in the code, to see if it should retry, op evaluates to not nil and hits the else, expecting the resource to be found (https://github.com/hashicorp/terraform-plugin-sdk/blob/master/helper/resource/state.go#L126).

This may explain it better: https://golang.org/doc/faq#nil_error

I'm not sure if it's always safe to assume that op will always be nil here, but it seems as though we want to retry, and in order to retry, this will need to return nil. However, with that logic, maybe line 134 should also return nil instead of op?

all: fixed an issue where operation retries were suppressed

[modular-magician]

Hi! I'm the modular magician, I work on Magic Modules.
I see that this PR has already had some downstream PRs generated. Any open downstreams are already updated to your most recent commit, 8cc3d7d.

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I built this PR into one or more new PRs on other repositories, and when those are closed, this PR will also be merged and closed.
depends: hashicorp/terraform-provider-google-beta#1494
depends: GoogleCloudPlatform/terraform-google-conversion#284
depends: hashicorp/terraform-provider-google#5134

[rileykarson]

This + modifying L134 seem correct to me. I'm curious if we ever expected to get non-nil op values returned when err wasn't nil. Most QueryOp implementations are just passing on another function's return, unfortunately.

[modular-magician]

Hi! I'm the modular magician, I work on Magic Modules.
I see that this PR has already had some downstream PRs generated. Any open downstreams are already updated to your most recent commit, 5d49869.

Pull request statuses

terraform-provider-google-beta already has an open PR.
terraform-google-conversion already has an open PR.
terraform-provider-google already has an open PR.
No diff detected in Ansible.
No diff detected in Inspec.

New Pull Requests

I didn't open any new pull requests because of this PR.