Allows 0 as certificate serial number

[joyantaDebnath]

You should not allow 0 (zero) as certificate serial number. RFC 5280 says, "The serial number MUST be a positive integer assigned by the CA to each cer- tificate...CAs MUST force the serial Number to be a non-negative integer...Non- conforming CAs may issue certificates with serial numbers that are negative or zero. Certificate users SHOULD be prepared to gracefully handle such certificates."