Fixes#149089 and #149700.
Before #145837, when processing a reduction symbol not yet supported by
OpenMP lowering, the reduction processor would simply skip filling in
the reduction symbols and variables. With #145837, this behvaior was
slightly changed because the reduction symbols are populated before
invoking the reduction processor (this is more convenient to shared the
code with `do concurrent`).
This PR restores the previous behavior.
(cherry picked from commit 36c37b019b5daae79785e8558d693e6ec42b0ebd)
4d6604adf1