🌱 Add linter to show nil panic. (#1960)

* 🌱 Add linter to show nil panic.

The code contained an obvious nil panic on err.Error()

```go
		err = action.Error()
		if err != nil {
			err = fmt.Errorf("action %+v failed (wait for rescue enabled): %w", action, err)
			s.scope.Error(err, "")
			err := s.scope.SetErrorAndRemediate(ctx, err.Error())
			if err != nil {
				return reconcile.Result{}, err
			}
			conditions.MarkFalse(hm, infrav1.ServerProvisionedCondition,
				"EnablingRescueActionFailed", clusterv1.ConditionSeverityWarning,
				"%s", err.Error())
			return reconcile.Result{}, nil
		}
```

No linter complained up to now.

Govet nilness does detect that now.

* Fix lint findings

* Fix CI failures

* Revert "Fix CI failures"

This reverts commit 3028076.

* Revert "Fix lint findings"

This reverts commit d7cd79b.

* Fix rescue action nil panic

Author: guettli

.golangci.yaml

@@ -40,6 +40,9 @@ linters:
     - unused
     - whitespace
   settings:
+    govet:
+      enable:
+        - nilness
     gocritic:
       disabled-checks:
         - appendAssign

pkg/services/hcloud/server/server.go

@@ -449,14 +449,15 @@ func (s *Service) handleBootStateEnablingRescue(ctx context.Context, server *hcl
 		err = action.Error()
 		if err != nil {
 			err = fmt.Errorf("action %+v failed (wait for rescue enabled): %w", action, err)
+			msg := err.Error()
 			s.scope.Error(err, "")
-			err := s.scope.SetErrorAndRemediate(ctx, err.Error())
-			if err != nil {
-				return reconcile.Result{}, err
+			remediateErr := s.scope.SetErrorAndRemediate(ctx, msg)
+			if remediateErr != nil {
+				return reconcile.Result{}, remediateErr
 			}
 			conditions.MarkFalse(hm, infrav1.ServerProvisionedCondition,
 				"EnablingRescueActionFailed", clusterv1.ConditionSeverityWarning,
-				"%s", err.Error())
+				"%s", msg)
 			return reconcile.Result{}, nil
 		}