Ignore nil objects occured when rendering a file

[vasrem]

This commits addresses an edge case where a nil object can occur while rendering a file. In that situation, in one of the places the renderer is used, it will try to add ownership to a nil object and fail.

Testing

Before:

$ go test ./pkg/render/ -run TestTemplateWithEmptyObject
--- FAIL: TestTemplateWithEmptyObject (0.00s)
    render_test.go:101:
        Expected
            <int>: 3
        to equal
            <int>: 2
FAIL
FAIL    github.com/k8snetworkplumbingwg/sriov-network-operator/pkg/render       0.019s
FAIL

[github-actions]

Thanks for your PR,
To run vendors CIs use one of:

• /test-all: To run all tests for all vendors.
• /test-e2e-all: To run all E2E tests for all vendors.
• /test-e2e-nvidia-all: To run all E2E tests for NVIDIA vendor.

To skip the vendors CIs use one of:

• /skip-all: To skip all tests for all vendors.
• /skip-e2e-all: To skip all E2E tests for all vendors.
• /skip-e2e-nvidia-all: To skip all E2E tests for NVIDIA vendor.
  Best regards.

[github-actions]

Thanks for your PR,
To run vendors CIs use one of:

• /test-all: To run all tests for all vendors.
• /test-e2e-all: To run all E2E tests for all vendors.
• /test-e2e-nvidia-all: To run all E2E tests for NVIDIA vendor.

To skip the vendors CIs use one of:

• /skip-all: To skip all tests for all vendors.
• /skip-e2e-all: To skip all E2E tests for all vendors.
• /skip-e2e-nvidia-all: To skip all E2E tests for NVIDIA vendor.
  Best regards.

[coveralls]

Pull Request Test Coverage Report for Build 7219210136

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 25.706%

---

Totals
Change from base Build 7020180866:	0.02%
Covered Lines:	2359
Relevant Lines:	9177

---

💛 - Coveralls

[zeeke]

nit: The problem this PR fixes occurs even without the dash (-):
i.e.:

{{ if .Enable }}
---
...

as the problem is related to the \n before ---, which ends up in a nil unstructured object.

BTW, the fix would remain the same. thanks for tackling this.
LGTM

[adrianchiris]

LGTM!