[FIX] Check for zero signature length
[FIX] Check for zero signature length

 - If the length of the client signature is zero, then the server
   should return Bad_ApplicationSignatureInvalid

Signed-off-by: Jayanth Velusamy <cc3e9f5840cd85783c661df2080d8099dc5077b9@kalycito.com>

JGrothoff/open62541,jpfr/open62541,StalderT/open62541,JGrothoff/open62541,open62541/open62541,open62541/open62541,JGrothoff/open62541,jpfr/open62541,jpfr/open62541,JGrothoff/open62541,open62541/open62541,StalderT/open62541,StalderT/open62541,StalderT/open62541,open62541/open62541,jpfr/open62541