fix: hovering .. no longer clears the preview pane

the .. row has no image/video/text of its own, so the preview fell through to the blank-everything branch — most noticeable on video projects, where the video would stop and vanish. now non-preview rows just leave whatever was last shown in place.

assets/js/filebrowser.js

@@ -49,7 +49,8 @@
     if (src) { showImg(src); hideTexts(); hidePlayer(); }
     else if (vid) { if (img) img.hidden = true; hideTexts(); showPlayer(); }
     else if (tkey) { if (img) img.hidden = true; hidePlayer(); showText(tkey); }
-    else { if (img) img.hidden = true; hideTexts(); hidePlayer(); }
+    // rows with no preview of their own (".." above all) leave whatever was
+    // last shown in place instead of blanking the pane out
 
     if (cap) {
       var n = a.querySelector(".tui__name");