add a little timeout to the delayed cw thing

it seems like sometimes the load handlers are processed before the
image is actually switched

script/single.ts

@@ -27,7 +27,8 @@ function setImage(id: string, src: string, href: string, cw: string): void {
 
   if (curCw && !coverNew) {
     // keep old cover until load
-    mainimg.addEventListener('load', () => openCW(null, curCw), {once: true});
+    function removeCover() { setTimeout(() => openCW(null, curCw!), 100); }
+    mainimg.addEventListener('load', removeCover, {once: true});
   } else if (coverNew) {
     // place new cover
     const newCw =