Predicting with function `arima` producing NaN values in R -

i using arima function intraday forecasting. data available every 15 minute in day. in code below, working fine except few values of in loop. output displayed i=223. predict function produces nan values. have checked dataset, there no nan value there. kindly suggest me how rid of problem.

predict1=c()  predict2=c()  for(i in 1:456){    y1n=ts(nbl$nbp[(12385+(i-1)*4):(15356+(i-1)*4)],frequency=96)    y1n[which(is.na(y1n))]=y1n[which(is.na(y1n))-96]    arima1=arima(y1n,order=c(1,1,0),seasonal=c(2,1,1),method="css")    predict1=predict(arima1,8)    predict2[(((i-1)*4)+1):(((i-1)*4)+4)]=predict1$pred[5:8]  }  arima1  call:  arima(x = y1n, order = c(1, 1, 0), seasonal = c(2, 1, 1), method = "css")  coefficients:           ar1     sar1     sar2     sma1           0.0241  -0.1122  -0.1068  -0.7830      s.e.    0.0188   0.0240   0.0224   0.0189   sigma^2 estimated 1490:  part log likelihood = -14583.05  > predict1=predict(arima1,8)  > predict1  $pred  time series:  start = c(31, 93)   end = c(32, 4)   frequency = 96   [1] nan nan nan nan nan nan nan nan   $se  time series:  start = c(31, 93)   end = c(32, 4)   frequency = 96   [1] nan nan nan nan nan nan nan nan