The program crashes when incomplete data is entered into Msg Parser

[raspopov]

1. Open "Modbus Message Parser" dialog box.
2. Type "00" (e.g. 1 byte).
3. Press the "Parse" button.
4. Crash.

Code analysis shows that the program crashes because it does not check the minimum size of the data entered by the user. Specifically, the program tries to calculate a checksum from two bytes, but only one is entered. This results in a negative length and an array index out-of-bounds error.

Version 1.12.0.