[3.11] gh-112087: Fix reduce logic for the empty reverse iterator for list

[corona10]

• Issue: Make list objects thread-safe in --disable-gil builds #112087

[corona10]

(.oss) ➜  cpython git:(gh-112087-3.11) ✗ ./python.exe -m test test_iter -R 3:3
Using random seed: 3663832972
Raised RLIMIT_NOFILE: 256 -> 1024
0:00:00 load avg: 6.95 Run 1 test sequentially
0:00:00 load avg: 6.95 [1/1] test_iter
beginning 6 repetitions
123456
......

== Tests result: SUCCESS ==

1 test OK.

Total duration: 1.1 sec
Total tests: run=56
Total test files: run=1/1
Result: SUCCESS