fix bug

The old code removed all non-ASCII characters.

Author: hjiayz

llama-cpp-2/src/model.rs

@@ -549,7 +549,7 @@ impl LlamaModel {
             if res > buff.len() as i32 {
                 return Err(ApplyChatTemplateError::BuffSizeError);
             }
-            String::from_utf8(buff.iter().filter(|c| **c > 0).map(|&c| c as u8).collect())
+            Ok::<String, ApplyChatTemplateError>(CStr::from_ptr(buff.as_mut_ptr()).to_string_lossy().to_string())
         }?;
         Ok(formatted_chat)
     }