Add nil check to recurring_schedule in google_os_config_patch_deployment

[modular-magician]

Fixes hashicorp/terraform-provider-google#7229

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Release Note Template for Downstream PRs (will be copied)

osconfig: fixed a potential crash in `google_os_config_patch_deployment` due to an unchecked nil value in `recurring_schedule`

Derived from GoogleCloudPlatform/magic-modules#3974