fix: guard org-drill-smart-reschedule cond against nil days-ahead

The function takes `days-ahead' as &optional, but the schedule cond
called `(= 0 days-ahead)' and `(cl-minusp days-ahead)' before any
type-guard, so passing nil crashed with a wrong-type-argument error.

Today's two callers (the rating-confirmation flow and the
org-drill-relearn-item helper) always pass a number, so this was
latent — but a third caller relying on the documented &optional
shape would hit it immediately.

Switched the cond to require numberp before the value comparisons,
and the default branch now falls back to the algorithm-computed
next-interval when days-ahead is nil.  That matches the intent
implied by the optional signature and the docstring.

0 files changed, 0 insertions, 0 deletions