input: Write a function to take in two strings as input and output a list of all the words in both strings. Return an empty list if any of the input strings are empty.
  assert string_to_list("I want to make a difference", "The journey to success is long") == ['I', 'want', 'to', 'make', 'a', 'difference', 'The', 'journey', 'to', 'success', 'is', 'long']
  assert string_to_list("I want to make a difference", "") == []
  assert string_to_list("", "The journey to success is long") == []
  assert string_to_list("", "") == []
  assert string_to_list("Hello World", "Python is fun") == ['Hello', 'World', 'Python', 'is', 'fun']
output: def string_to_list(str1, str2):
      if not str1 or not str2:
          return []
      words1 = str1.split()
      words2 = str2.split()
      return words1 + words2