Json cannot read property of undefined - node.js

Question

When I execute a command (the error doesn't occur when I type a normal message) in my discord bot I get an error saying:
Cannot read property 'active' of undefined
And it occurs when I try to console log an object from a json file where I store users data.
Those are the first lines of code of the index.js file of my bot, the line where I try to console log is where the error occurs
const Discord = require('discord.js');
const client = new Discord.Client();
const fs = require("fs");
const prefix = '>';
let xp = require("./storage/dbGeneral.json");
let pr = require("./storage/dbPremium.json");
let lv = require("./storage/levels.json");
client.on('message', message => {
console.log(pr[message.author.id].active);
}
This is the json file where I store the data
{
"397387465024864257": {
"active": false,
"dateStart": "",
"dateEnd": ""
}
}
This is the error:
index.js:14
console.log(pr[message.author.id].active);
^
TypeError: Cannot read property 'active' of undefined
at Client.client.on.message (index.js:14:39)
at emitOne (events.js:116:13)
at Client.emit (events.js:211:7)
at MessageCreateHandler.handle (\node_modules\discord.js\src\client\websocket\packets\handlers\MessageCreate.js:9:34)
at WebSocketPacketManager.handle (\node_modules\discord.js\src\client\websocket\packets\WebSocketPacketManager.js:103:65)
at WebSocketConnection.onPacket (\node_modules\discord.js\src\client\websocket\WebSocketConnection.js:333:35)
at WebSocketConnection.onMessage (\node_modules\discord.js\src\client\websocket\WebSocketConnection.js:296:17)
at WebSocket.onMessage (\node_modules\ws\lib\event-target.js:120:16)
at emitOne (events.js:116:13)
at WebSocket.emit (events.js:211:7)
I really don't know what is the cause of the error, all other json requests work fine with the same method.

Answer 1

The error is caused by trying to access a property of something not defined.
To fix your problem, you must check if the user exists in your database.
let user = pr[message.author.id];
if(user) console.log(user.active)