fix: initialize default metadata with all required fields (#6583)

Co-authored-by: openhands <openhands@all-hands.dev>

evaluation/benchmarks/swe_bench/eval_infer.py

@@ -412,6 +412,17 @@ if __name__ == '__main__':
         with open(metadata_filepath, 'r') as metadata_file:
             data = metadata_file.read()
             metadata = EvalMetadata.model_validate_json(data)
+    else:
+        # Initialize with a dummy metadata when file doesn't exist
+        metadata = EvalMetadata(
+            agent_class="dummy_agent",  # Placeholder agent class
+            llm_config=LLMConfig(model="dummy_model"),  # Minimal LLM config
+            max_iterations=1,  # Minimal iterations
+            eval_output_dir=os.path.dirname(args.input_file),  # Use input file dir as output dir
+            start_time=time.strftime('%Y-%m-%d %H:%M:%S'),  # Current time
+            git_commit=subprocess.check_output(['git', 'rev-parse', 'HEAD']).decode('utf-8').strip(),  # Current commit
+            dataset=args.dataset  # Dataset name from args
+        )
 
     # The evaluation harness constrains the signature of `process_instance_func` but we need to
     # pass extra information. Build a new function object to avoid issues with multiprocessing.