Fix KeyError in failing nightly (#1866)

SUMMARY:
Fixes:
https://github.com/neuralmagic/llm-compressor-testing/actions/runs/17901928706/job/50896401512

Restores previous behavior before #1844 merged.

Signed-off-by: Fynn Schmitt-Ulms <fschmitt@redhat.com>

Author: fynnsu

tests/llmcompressor/transformers/finetune/test_oneshot_and_finetune.py

@@ -101,7 +101,7 @@ def test_oneshot_and_finetune_gpu(config, tmp_path):
     model = config["model"]
     dataset = config["dataset"]
     recipe = config["recipe"]
-    dataset_config_name = config["dataset_config_name"]
+    dataset_config_name = config.get("dataset_config_name")
     num_train_epochs = config["num_train_epochs"]
     concat_txt = config["concat_txt"]
     output = tmp_path / "finetune_output"