Transaction struck at never ending while loop on incomplete response

[dhoomakethu]

Modbus TK sends error response without CRC and this response would make the pymodbus client struck in never ending read mode .

[dhoomakethu]

This is not exactly a bug from pymodbus per se , this is actually because ModbusTK sends error response without address and CRC and pymodbus expects those two fields to validate an error response. But better to handle this case from with in pymodbus as well