handle actions without config block

internal/terraform/node_action_instance.go

@@ -12,6 +12,7 @@ import (
 	"github.com/hashicorp/terraform/internal/lang/langrefs"
 	"github.com/hashicorp/terraform/internal/providers"
 	"github.com/hashicorp/terraform/internal/tfdiags"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // NodeActionDeclarationInstance represents an action in a particular module.
@@ -78,11 +79,15 @@ func (n *NodeActionDeclarationInstance) Execute(ctx EvalContext, _ walkOperation
 	allInsts := ctx.InstanceExpander()
 	keyData := allInsts.GetActionInstanceRepetitionData(n.Addr)
 
-	configVal, _, configDiags := ctx.EvaluateBlock(n.Config.Config, schema.ConfigSchema.DeepCopy(), nil, keyData)
+	configVal := cty.NullVal(schema.ConfigSchema.ImpliedType())
+	if n.Config.Config != nil {
+		var configDiags tfdiags.Diagnostics
+		configVal, _, configDiags = ctx.EvaluateBlock(n.Config.Config, schema.ConfigSchema.DeepCopy(), nil, keyData)
 
-	diags = diags.Append(configDiags)
-	if diags.HasErrors() {
-		return diags
+		diags = diags.Append(configDiags)
+		if diags.HasErrors() {
+			return diags
+		}
 	}
 
 	ctx.Actions().AddActionInstance(n.Addr, configVal, n.ResolvedProvider)