Align common definitions

packages/util/src/ext/error.ts

@@ -34,8 +34,7 @@ export default class ExtError extends Error implements ExtErrorInterface {
   // @ts-ignore we are assigning it via extend
   public code: number;
 
-  // @ts-ignore we are assigning it via extend
-  public data: number | string | undefined;
+  public data?: number | string;
 
   // @ts-ignore we are assigning it via extend
   public message: string;

packages/util/src/types.ts

@@ -6,7 +6,7 @@ import BN from 'bn.js';
 
 export interface ExtErrorInterface {
   code: number;
-  data: string | number;
+  data?: string | number;
   message: string;
   stack: string;
 }