fix: null guard in hideCtxMenu and scroll/touchmove listeners

hideCtxMenu now guards against null #ctx-menu element. scroll/touchmove
listeners only fire when menu is actually visible, preventing spurious
calls on every scroll event.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ui.js

@@ -153,13 +153,21 @@ export function showCtxMenu(e, song, list, idx) {
 }
 export function hideCtxMenu() {
   const m = document.getElementById('ctx-menu');
+  if (!m) return;
   m.style.display='none'; m.innerHTML='';
 }
 document.addEventListener('click', e => {
-  if(!document.getElementById('ctx-menu').contains(e.target)) hideCtxMenu();
+  const m = document.getElementById('ctx-menu');
+  if (m && !m.contains(e.target)) hideCtxMenu();
 });
-document.addEventListener('scroll', () => hideCtxMenu(), { passive: true, capture: true });
-document.addEventListener('touchmove', () => hideCtxMenu(), { passive: true, capture: true });
+document.addEventListener('scroll', () => {
+  const m = document.getElementById('ctx-menu');
+  if (m && m.style.display !== 'none') hideCtxMenu();
+}, { passive: true, capture: true });
+document.addEventListener('touchmove', () => {
+  const m = document.getElementById('ctx-menu');
+  if (m && m.style.display !== 'none') hideCtxMenu();
+}, { passive: true, capture: true });
 document.addEventListener('keydown', e => { if(e.key==='Escape') hideCtxMenu(); });
 
 // ─── PLAYLIST MODAL (Add to / Create) ───