ERROR
(node:9308) UnhandledPromiseRejectionWarning: TypeError: Supplied parameter was neither a Role nor a Snowflake.
    at GuildMember.addRole (C:\Users\annma\Desktop\Projects\Bots\Discord\TT\node_modules\discord.js\src\structures\GuildMember.js:440:38)
    at Client.bot.on (C:\Users\annma\Desktop\Projects\Bots\Discord\TT\index.js:56:16)
    at emitOne (events.js:116:13)
    at Client.emit (events.js:211:7)
    at MessageCreateHandler.handle (C:\Users\annma\Desktop\Projects\Bots\Discord\TT\node_modules\discord.js\src\client\websocket\packets\handlers\MessageCreate.js:9:34)
    at WebSocketPacketManager.handle (C:\Users\annma\Desktop\Projects\Bots\Discord\TT\node_modules\discord.js\src\client\websocket\packets\WebSocketPacketManager.js:103:65)
    at WebSocketConnection.onPacket (C:\Users\annma\Desktop\Projects\Bots\Discord\TT\node_modules\discord.js\src\client\websocket\WebSocketConnection.js:333:35)
    at WebSocketConnection.onMessage (C:\Users\annma\Desktop\Projects\Bots\Discord\TT\node_modules\discord.js\src\client\websocket\WebSocketConnection.js:296:17)
    at WebSocket.onMessage (C:\Users\annma\Desktop\Projects\Bots\Discord\TT\node_modules\ws\lib\event-target.js:120:16)
    at emitOne (events.js:116:13)
(node:9308) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:9308) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

CODE
	if(cmd === `${prefix}addRole`){
		let userToModify = message.mentions.members.first();
		let roleToAdd = message.mentions.roles.first();
		return userToModify.addRole(roleToAdd);
	}