Error Crawling Data Twitter With R Studio

[students12341]

how to fix an error like this

library(twitteR)
library(ROAuth)
customer_key<-"-aaaaaa"
customer_secret<-"aaaaaaaa"
access_token<-"212123213-aaaaa"
access_secret<-"ccccccccccccc"
setup_twitter_oauth(customer_key,customer_secret,access_token,access_secret)
Tweets = searchTwitter("anxiety", n=100, lang = "en")
Error: invalid assignment for reference class field ‘language’, should be from class “character” or a subclass (was class “NULL”)

I User RStudio for run this source code, this is my first time using the twitter API. before I saw the tutorial and they succeeded, after I tried it and there was an error like that. thankyou