Unable to get total

1. What is the problem? Be very detailed.
there are two integer fields "R1_1" and "R1_2",total sum of both the fields must be equal to 100
but if add score 100 to "R1_1" and leave "R1_2" blank or vice versa then i am unable to get total score could you please provide me the solution.

2. What app or server are you using and on what device and operating system? Include version numbers.

ODK Collect, Aggregate

3. What you have you tried to fix the problem?

4. What steps can we take to reproduce the problem?
Xlsform attached for your reference
script.xlsx (12.8 KB)

5. Anything else we should know or have? If you have a test form or screenshots or logs, attach below.

Convert blank into '0' because blank cannot be use in sum. Use this calculation


I hope it will work.