input: Write a function to filter out all negative numbers from a given matrix and set them to 0. The function should return the modified matrix. If the given matrix is empty, it should return an empty list.
  assert filter_out_negative([[-1, 2, -3], [-4, 5, 6], [-7, 8, 9]])==[[0, 2, 0], [0, 5, 6], [0, 8, 9]]
  assert filter_out_negative([[-1, -2, -3]])==[[0, 0, 0]]
  assert filter_out_negative([[1, 2, 3], [4, 5, 6]])==[[1, 2, 3], [4, 5, 6]]
  assert filter_out_negative([[]])==[[]]
  assert filter_out_negative([])==[]
output: def filter_out_negative(matrix):
      if not matrix:
          return []
      return [[0 if x < 0 else x for x in row] for row in matrix]