fixed zero index problem where _u8ResponseBufferLength is set.

[intelligentandgoodlooking]

Description

when a 1 word (2 byte) response is received _u8ResponseBufferLength is erroneously set to 0 instead of 1 similarly, a 16 word (32 byte) response is received, _u8ResponseBufferLength is set to 15 instead of 16. This causes available() to return 1 less than it should.

Issues Resolved

It seems like not many people use the available() function.

Check List

General

• [ ] Code follows coding style defined in STYLE.md
• [ ] Doxygen comments are included inline with code
• [ ] No unnecessary whitespace; check with git diff --check before committing.

The following have been modified to reflect new features, if warranted

• [ ] README.md
• [ ] keywords.txt (use tabs as whitespace separators)
• [ ] library.properties
• [ ] examples/ - update or create new ones, as warranted

The following have NOT been modified

• [ ] doc/ - will be updated upon versioned release
• [ ] .ruby-gemset
• [ ] .ruby-version
• [ ] CHANGELOG.md - will be updated upon versioned release (HISTORY.md is deprecated)
• [ ] Gemfile
• [ ] LICENSE
• [ ] VERSION - will be updated upon versioned release

[PBudmark]

Yes, the _u8ResponseBufferLength needs the stepup, but to avoid buffer overrun, the assignment should be moved inside brackets at 'if (i < ku8MaxBufferSize)' or else _u8ResponseBufferLength is increased even if no register is stored.

In the case with odd number of bytes, 'if (u8ModbusADU[2] % 2)', _u8ResponseBufferLength = i + 1; should be done inside the brackets, as i is already stepped from the for-statement.