This is a cherry-pick of #9135

This fix applies the same safety check that was added to v1 pipelines in PR #8089. The validateMatrixedPipelineTaskConsumed function was panicking when encountering invalid variable substitutions like "$(tasks)-$(tasks.echo-result.results.output)" because it tried to access subExpressions[1] without first checking if the expression was a valid result reference.

The fix adds a check to skip expressions that don't look like result references before attempting to parse them, preventing the panic and allowing the webhook to return a proper validation error instead.

Related: #8089

Changes

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Release Notes

Resolved an issue where Pipelines with invalid result references in matrix parameters would cause a panic during validation (v1beta1 API)