fix: omit :foreground from emoji icon face when no color provided

The font branch of wttrin--make-emoji-icon built its face plist with `:foreground foreground` even when foreground was nil, producing a literal `(:family ... :height 1.0 :foreground nil)`. The mode-line redisplays many times per second, and Emacs validates faces on every redisplay. A single fresh-cache state produced hundreds of "Invalid face attribute :foreground nil" warnings in *Messages*. The bug's been live since 2026-02-21 (b74b98f). The 130bbc07 helper extraction kept it in place.

Switch to backquote splicing so the :foreground key is included only when foreground is non-nil. Behavior is identical on the colored path. On the nil path the emoji renders with the default mode-line color, the same visible result as before, without the warning flood.

0 files changed, 0 insertions, 0 deletions