WebUI: fix failed conversion to number

The value has unit suffix (`px`) and require using `parseInt()` for conversion.

Fix up f73f31619d.
PR #21862.

src/webui/www/private/scripts/dynamicTable.js

@@ -254,7 +254,7 @@ window.qBittorrent.DynamicTable ??= (() => {
             const onStart = function(el, event) {
                 if (this.canResize) {
                     this.currentHeaderAction = "resize";
-                    this.startWidth = Number(this.resizeTh.style.width);
+                    this.startWidth = parseInt(this.resizeTh.style.width, 10);
                 }
                 else {
                     this.currentHeaderAction = "drag";