Compression: Prevent undefined behavior when feeding empty input
Compression: Prevent undefined behavior when feeding empty input

&emptyVector[n] triggers undefined behavior because it is an out-of-
bounds access, even if n == 0. emptyVector.data() does not (but may
return nullptr).

randombit/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,randombit/botan,webmaster128/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,webmaster128/botan