Update CrackDetection.java

Note: Crack detection analysis is applied only for FFT results of 1 audio channels (not two audio channels)
double[] magnitude;  - this array must become 2-dimensional 

Also change: 
magnitude[0][cnt] = (Math.sqrt(FFT.realOut[0] [cnt] * FFT.realOut [0] [cnt]
				           + FFT.imagOut[0] [cnt] * FFT.imagOut[0] [cnt])) / iData_Length;

magnitude[1][cnt] = (Math.sqrt(FFT.realOut[1] [cnt] * FFT.realOut [1] [cnt]
				           + FFT.imagOut[1] [cnt] * FFT.imagOut[1] [cnt])) / iData_Length;