Fix msg type

gramjs/client/telegramBaseClient.ts

@@ -121,7 +121,7 @@ const clientParamsDefault = {
             : false,
 };
 
-export class TelegramBaseClient {
+export abstract class TelegramBaseClient {
     /** The current gramJS version. */
     __version__ = version;
     /** @hidden */

gramjs/tl/custom/message.ts

@@ -798,7 +798,8 @@ export class Message extends Mixin(SenderGetter, ChatGetter) {
     }
 
     async downloadMedia(params: DownloadMediaInterface) {
-        if (this._client) return this._client.downloadMedia(this, params);
+        // small hack for patched method
+        if (this._client) return this._client.downloadMedia(this as any, params);
     }
 
     /* TODO doesn't look good enough.