#1258: lands.first() instead of lands[0] (a transition with no endpoints can't panic)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/panels/timeline.rs

@@ -1903,7 +1903,7 @@ fn move_transition_preview(app: &FilmcraftApp, seq: &Sequence, trn: &filmcraft_p
     if lands.len() != endpoints.len() {
         return None;
     }
-    let (dest, delta) = lands[0];
+    let &(dest, delta) = lands.first()?;
     lands.iter().skip(1).all(|l| *l == (dest, delta)).then(|| (trn.start + delta, trn.end() + delta, dest))
 }