Add guards in case when "octets" attribute has size

[lemenkov]

dictionaries/dictionary.microsoft:ATTRIBUTE MS-CHAP-Response 1 octets[50]
dictionaries/dictionary.microsoft:ATTRIBUTE MS-CHAP-CPW-1 3 octets[70]
dictionaries/dictionary.microsoft:ATTRIBUTE MS-CHAP-CPW-2 4 octets[84]
dictionaries/dictionary.microsoft:ATTRIBUTE MS-CHAP2-Response 25 octets[50]
dictionaries/dictionary.microsoft:ATTRIBUTE MS-CHAP2-CPW 27 octets[68]
dictionaries/dictionary.microsoft:#ATTRIBUTE MS-ARAP-Challenge 33 octets[8]
dictionaries/dictionary.rfc2869:ATTRIBUTE ARAP-Password 70 octets[16]
dictionaries/dictionary.rfc2869:ATTRIBUTE ARAP-Features 71 octets[14]
dictionaries/dictionary.rfc2869:ATTRIBUTE ARAP-Challenge-Response 84 octets[8]