MinGW gcc emits -Wmaybe-uninitialized for `digs[0]` in the
`mrb_format_float` function because it cannot prove that
`count_digits()` always returns >= 1. The code is correct
(count_digits's `d == 0` early return makes the lower bound
clear to a human reader), but gcc's flow analysis does not
follow through. Initialize `digs` to silence the false positive
across all MinGW gcc CI configurations.
Co-authored-by: Claude <noreply@anthropic.com>
Yukihiro "Matz" Matsumoto
ad0ea8571f