validateVisitGroupField missing to interate to next field for else case, which fault lead "Incorrect NumInGroup"

[gpmn]

https://github.com/quickfixgo/quickfix/blob/bbe42d9f62205321fa6b61c46f22fe073b814467/validation.go#L215

missing a line like this: fieldStack = fieldStack[1:]

fieldStack not iterated to it's next element, that's why quickfix raised such error "Incorrect NumInGroup count for repeating group"

this is the original:

https://github.com/quickfixgo/quickfix/issues/365