fix(report): fix error if miconfigs are empty

[DmitriyLewen]

Description

After #5767 Trivy returns error if misconfigs are empty:

  - template: output template:17:44: executing "output template" at <.MisconfSummary.Successes>: nil pointer evaluating *types.MisconfSummary.Successes

.MisconfSummary is pointer. Therefore we need to add check to number of misconfigs.

Related PRs

• fix(report): don't mark misconfig passed tests as failed in junit.tpl #5767

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