Cannot read property 'substr' of undefined#207

I'm pretty sure I give it a string, but it should be that or something else.. But also, `substr`? ```js C:\Users\Vlad\Desktop\New folder (2)\node_modules\string\lib\string.js:86 return new this.constructor(this.s.substr(0, 1).toUpperCase() + this.s.substring(1).toLowerCase()); ^ TypeError: Cannot read property 'substr' of undefined at S.capitalize (C:\Users\Vlad\Desktop\New folder (2)\node_modules\string\lib\string.js:86:41) at unirest.get.headers.end.res (C:\Users\Vlad\Desktop\New folder (2)\Commands\Public\e621.js:43:43) at Request.handleRequestResponse [as _callback] (C:\Users\Vlad\Desktop\New folder (2)\node_modules\unirest\index.js:463:26) at Request.self.callback (C:\Users\Vlad\Desktop\New folder (2)\node_modules\unirest\node_modules\request\request.js:187:22) at emitTwo (events.js:106:13) at Request.emit (events.js:194:7) at Request.<anonymous> (C:\Users\Vlad\Desktop\New folder (2)\node_modules\unirest\node_modules\request\request.js:1044:10) at emitOne (events.js:96:13) at Request.emit (events.js:191:7) at IncomingMessage.<anonymous> (C:\Users\Vlad\Desktop\New folder (2)\node_modules\unirest\node_modules\request\request.js:965:12) at emitNone (events.js:91:20) at IncomingMessage.emit (events.js:188:7) at endReadableNT (_stream_readable.js:975:12) at _combinedTickCallback (internal/process/next_tick.js:80:11) at process._tickDomainCallback (internal/process/next_tick.js:128:9) ```