iOS Audiokit FFTTap BufferSize Exception Error

Question

I am trying to use fftTap from iOS microphone with AudioKit, and here is the code

fft = FFTTap(highPassFilter2!, bufferSize: 8192 * 4, fftValidBinCount: nil, handler: {data in})

I tried using a bufferSize of 8192 * 4, which has allowed me to detect HZ at intervals of about 1.3 (Sample Rate is 44100, 44100 / (8192 * 4) = 1.34582519531, am I correct?) but I always get the exception error in File BaseTap around line 90.

private func handleTapBlock(buffer: AVAudioPCMBuffer, at time: AVAudioTime) {
        // Call on the main thread so the client doesn't have to worry
        // about thread safety.
        buffer.frameLength = bufferSize <<<<< here

The log shows

libc++abi: terminating with uncaught exception of type NSException
*** Terminating app due to uncaught exception 'com.apple.coreaudio.avfaudio', reason: 'required condition is false: length <= _imp->_frameCapacity'
terminating with uncaught exception of type NSException

It seems not work, but I want to be able to capture the accuracy less than 2 Hz, is there any way to try?

Really Thanks.