fix(workflow): panic error in exit node (#2105)

backend/domain/workflow/internal/nodes/exit/exit.go

@@ -82,8 +82,10 @@ func (c *Config) Adapt(_ context.Context, n *vo.Node, _ ...nodes.AdaptOption) (*
 			return nil, fmt.Errorf("exit node's content value type must be %s, got %s", vo.BlockInputValueTypeLiteral, content.Value.Type)
 		}
 
+		if content.Value.Content != nil {
 			c.Template = content.Value.Content.(string)
 		}
+	}
 
 	if n.Data.Inputs.TerminatePlan == nil {
 		return nil, fmt.Errorf("exit node requires a TerminatePlan")