input: Write a function to filter out all negative numbers from the given matrix and replace them with 0. The matrix should be processed in place. If the matrix is empty, return an empty matrix.
  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], [-4, 5, -6], [7, -8, 9]])==[[1, 0, 3], [0, 5, 0], [7, 0, 9]]
  assert filter_out_negative([[-1, -2, -3], [-4, -5, -6], [-7, -8, -9]])==[[0, 0, 0], [0, 0, 0], [0, 0, 0]]
  assert filter_out_negative([])==[]
output: def filter_out_negative(matrix):
      if not matrix:
          return []
      for i in range(len(matrix)):
          for j in range(len(matrix[i])):
              if matrix[i][j] < 0:
                  matrix[i][j] = 0
      return matrix