message: fix: Member#guildMember return type
diff: @@ -134,7 +134,7 @@ export interface Member {
  /** Get the nickname or the username if no nickname */
  name(guildID: string): string;
  /** Get the nickname */
  - guildMember(guildID: string): GuildMember;
  + guildMember(guildID: string): GuildMember | undefined;
  /** Send a direct message to the user is possible */
  sendDM(content: string | MessageContent): Promise<any>;
  /** Kick the member from a guild */
  