scripts : exit compare-llama-bench.py gracefully when there's nothing to compare (ggml-org#13451)

Author: CISC

scripts/compare-llama-bench.py

@@ -318,7 +318,7 @@ def get_rows(properties):
 
     show = []
     # Show CPU and/or GPU by default even if the hardware for all results is the same:
-    if "n_gpu_layers" not in properties_different:
+    if rows_full and "n_gpu_layers" not in properties_different:
         ngl = int(rows_full[0][KEY_PROPERTIES.index("n_gpu_layers")])
 
         if ngl != 99 and "cpu_info" not in properties_different:
@@ -338,6 +338,10 @@ def get_rows(properties):
             pass
     rows_show = get_rows(show)
 
+if not rows_show:
+    logger.error(f"No comparable data was found between {name_baseline} and {name_compare}.\n")
+    sys.exit(1)
+
 table = []
 for row in rows_show:
     n_prompt = int(row[-5])