bug fixes

lib/tools/data_loader.py

@@ -6,6 +6,12 @@ import pandas as pd
 
 
 def load_sqlite_to_dataframe(db_path:str, query:str) -> pd.DataFrame:
+    df: pd.DataFrame = pd.DataFrame()
+    import os
+    if not os.path.exists(db_path):
+        print(f"WARNING: database file {db_path} does not exist")
+        return df
+
     try:
         conn = sqlite3.connect(db_path)