* common: add bounds check in common_init_result::sampler to prevent segfault on failed model load
* Revert a308e584ca
* Add regression test
* Remove regression test for init-fail sampler check
The embd.begin(), embd.begin() range is empty and inserts nothing, so session_tokens never gets updated after
decoding. Should be embd.begin(), embd.end(). Introduced in commit 2b6dfe8.