Variable Length file processing error

## Describe the bug
Getting Exception while processing the Variable length source file , while using Cobrix

BDW headers contain non-zero values where zeros are expected (check 'rdw_big_endian' flag. Header: 196,197,0,12, offset: 0.

## Code snippet that caused the issue

```
df= spark.read.format("cobol").option("copybook", "/cobrix/copybook/copybook.txt")\
.option("record_format", "VB").option("is_rdw_big_endian", "false")\
.load("/cobrix/data/datapath")
df.show()
```

## Expected behavior
A clear and concise description of what you expected to happen.
Parse the copybook and variable length source files and display the results.

## Context
- Cobrix version:cobol-parser_2.12-2.6.2.jar
- Spark version:3.1.1
- Scala version:3.1.1
- Operating system:Linux

## Copybook (if possible)
```
01 REPORT-TAPE-DETAIL-RECORD.
02 VXT-REC-CODE-BYTES. 00000130
03 VXT-REC-CODE-KEY PIC X. 00000140
03 VXT-REC-TYPE-CONTROL PIC X. 00000150
01.021 03 VXT-XFER-KEY. 00000160
01.021 04 VXT-NO-POST-REASON PIC S9(3)V COMP-3.00000170
02 VXT-SPECIAL-ACCT-BYTES. 00000180
03 VXT-SC-1 PIC X. 00000190
03 VXT-SC-2 PIC X. 00000200
03 VXT-SC-3 PIC X. 00000210
03 VXT-SC-4 PIC X. 00000220
03 VXT-SC-5 PIC X. 00000230
03 VXT-SC-6 PIC X. 00000240
03 VXT-SC-7 PIC X. 00000250
03 VXT-SC-8 PIC X. 00000260
02 VXT-RPT-FULL-ACCT-NO. 00000270
03 VXT-RPT-SYSTEM-BANK. 00000280
04 VXT-RPT-SYSTEM-NO PIC XXXX. 00000290
04 VXT-RPT-BANK-NO. 00000300
05 VXT-RPT-PRIN-BANK PIC XXXX. 00000310
05 VXT-RPT-AGENT-BANK PIC XXXX. 00000320
03 VXT-RPT-RECEIPT-NUMBER PIC X(16). 00000330
02 VXT-RECEIPT-CODE PIC S9(3)V COMP-3.00000340
02 VXT-MRCH-FULL-ACCT-NO. 00000350

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