ensure that torch is not used unless it is available (#467)

Author: svlandeg

spacy_llm/models/hf/stablelm.py

@@ -2,11 +2,11 @@
 
 from confection import SimpleFrozenDict
 
-from ...compat import Literal, has_transformers, torch, transformers
+from ...compat import Literal, has_torch, has_transformers, torch, transformers
 from ...registry.util import registry
 from .base import HuggingFace
 
-if has_transformers:
+if has_transformers and has_torch:
 
     class _StopOnTokens(transformers.StoppingCriteria):
         def __call__(