The IES parser in Cycles would lead to heap buffer overflow error
when non-supported or invalid data is provided to it.
The error was caused by the way how stirng is copied to vector
skipping the last null-terminator. Later C-style string utilities
are used for parsing, and they expect the data to be null-terminated.
It is unclear why data needs to be stored as vector: storing it as
string simplifies initialization.
Easiest to reproduce the issue is to use Blender build with address
sanitizer enabled.
Pull Request: https://projects.blender.org/blender/blender/pulls/116752
