fix: Check for existence of clip model path (#1264)

Author: kejcao

llama_cpp/llama_chat_format.py

@@ -1848,6 +1848,9 @@ def __init__(self, clip_model_path: str, verbose: bool = False):
         self.verbose = verbose
         self._clip_free = self._llava_cpp._libllava.clip_free  # type: ignore
 
+        if not os.path.exists(clip_model_path):
+            raise ValueError(f"Clip model path does not exist: {clip_model_path}")
+
         with suppress_stdout_stderr(disable=self.verbose):
             self.clip_ctx = self._llava_cpp.clip_model_load(
                 self.clip_model_path.encode(), 0