error rather than panic when workflow action index is invalid

Signed-off-by: Marques Johansson <[email protected]>

grpc-server/tinkerbell.go

@@ -22,6 +22,7 @@ const (
 	errInvalidActionName     = "invalid action name"
 	errInvalidTaskReported   = "reported task name does not match the current action details"
 	errInvalidActionReported = "reported action name does not match the current action details"
+	errInvalidActionIndex    = "invalid action index for workflow"
 
 	msgReceivedStatus   = "received action status: %s"
 	msgCurrentWfContext = "current workflow context"
@@ -111,6 +112,9 @@ func (s *server) ReportActionStatus(ctx context.Context, req *pb.WorkflowActionS
 			actionIndex++
 		}
 	}
+	if actionIndex == wfContext.TotalNumberOfActions-1 {
+		return nil, status.Errorf(codes.FailedPrecondition, errInvalidActionIndex)
+	}
 	action := wfActions.ActionList[actionIndex]
 	if action.GetTaskName() != req.GetTaskName() {
 		return nil, status.Errorf(codes.InvalidArgument, errInvalidTaskReported)