Fix canceling file selector on Windows Edge sometimes blocks UI (#257)

public/scripts/ui.js

@@ -675,6 +675,8 @@ class PeerUI {
         const $input = e.target;
         const files = $input.files;
 
+        if (files.length === 0) return;
+
         Events.fire('files-selected', {
             files: files,
             to: this._peer.id