fix json parsing error

dist/index.js

@@ -47,8 +47,8 @@ export class TetherClient {
             mutation_id: mutation_id
         }));
         return new Promise((resolve, reject) => {
-            this.websocketHandler.onMutation = (data) => {
-                if (data.mutation_id === mutation_id) {
+            this.websocketHandler.onMutation = (mutation_id, data) => {
+                if (mutation_id === mutation_id) {
                     resolve(data);
                 }
             };

dist/utils/websocket.d.ts

@@ -8,7 +8,7 @@ export declare class WebSocketHandler {
     private maxReconnectAttempts;
     private reconnectInterval;
     private sendQueue;
-    onMutation: (data: any) => void;
+    onMutation: (mutation_id: string, data: any) => void;
     startConnection: (url: string) => void;
     attemptReconnect: () => void;
     close: () => void;

dist/utils/websocket.js

@@ -28,7 +28,7 @@ export class WebSocketHandler {
                 this.onQuery(data.location, data.data);
             }
             else if (data.type === 'mutation') {
-                this.onMutation(data.data);
+                this.onMutation(data.mutation_id || '', data.data);
             }
             else if (data.type === 'error') {
                 console.error(data.error);