weeklyreview adds an empty line before adding the action

[arcturus140]

I have one action in my tickler file:

+p8 @call a friend start:2019-01-01 repeat:wednesday due:today

which adds the line to my todo.txt:

2021-03-10 +p8 @call a friend due:2021-03-11 t:2021-03-10

but it also adds an empty line. After running the script multiple times with different tickler, i get:

2021-03-10 +p5 @call a friend due:2021-03-11 t:2021-03-10 

2021-03-10 +p6 @call a friend due:2021-03-11 t:2021-03-10 

2021-03-10 +p7 @call a friend due:2021-03-11 t:2021-03-10 

because of

if firsttime:
  todo.write('\n')

what is the reason for this empty line?