fix: do not run post step if no step result is available

Having no step result means we do not run any step (neither pre
nor main) and we do not need to run post.

pkg/runner/action.go

@@ -428,8 +428,14 @@ func shouldRunPostStep(step actionStep) common.Conditional {
 	return func(ctx context.Context) bool {
 		log := common.Logger(ctx)
 		stepResults := step.getRunContext().getStepsContext()
+		stepResult := stepResults[step.getStepModel().ID]
 
-		if stepResults[step.getStepModel().ID].Conclusion == model.StepStatusSkipped {
+		if stepResult == nil {
+			log.Debugf("skip post step for '%s'; step was not executed", step.getStepModel())
+			return false
+		}
+
+		if stepResult.Conclusion == model.StepStatusSkipped {
 			log.Debugf("skip post step for '%s'; main step was skipped", step.getStepModel())
 			return false
 		}