input: Write a function to convert a given SQL statement into a Python Pandas DataFrame. The function should take in an SQL query string and a database connection object, and return a Pandas DataFrame containing the result of the SQL query. If the SQL query is empty, return an empty DataFrame.
  
  assert convert_sql_to_df("SELECT * FROM book;", conn).equals(pd.read_sql_query("SELECT * FROM book;", conn))==True
  assert convert_sql_to_df("SELECT title, author FROM book WHERE year > 2000;", conn).equals(pd.read_sql_query("SELECT title, author FROM book WHERE year > 2000;", conn))==True
  assert convert_sql_to_df("", conn).empty==True
  assert convert_sql_to_df("SELECT * FROM nonexistent_table;", conn).empty==True
output: def convert_sql_to_df(sql_query, conn):
      if not sql_query:
          return pd.DataFrame()
      try:
          return pd.read_sql_query(sql_query, conn)
      except:
          return pd.DataFrame()