check if wave files have been opened sucessfully in the converter program

    printf( "In %d, Out: %d\n", in_format, out_format );

    wavFile_in = OpenWav( fileName_in, &samplingRate, &numChannels, &samplesInFile, &bps );

    if ( !wavFile_in )

    {

        fprintf( stderr, "Failed to open input wav file: %s\n", fileName_in );

        return -1;

    }

    wavFile_out = CreateWav( fileName_out, samplingRate, numChannels, 16 );

    if ( !wavFile_out )

    {

        fprintf( stderr, "Failed to open output wav file: %s\n", fileName_out );

        return -1;

    }

    order = (int16_t) sqrtf( numChannels ) - 1;

    assert( order > 0 && order <= 3 );