[flang] [llvm] [flang][runtime] Handle null list-directed fields in child input (PR #155707)

[Daniel Chen via llvm-commits]

DanielCChen wrote:

> The reducer in the issue still fails. I updated the description of the issue with the expected output.

To clarify,
The output from the 1st read statement is still incorrect after this patch.
Flang still produces `1 3 4` where the expected output is `1 -1 3`

https://github.com/llvm/llvm-project/pull/155707