Issue #3488464: Added check to not write value prop if not visible:

This should remove the lingering custom property in various edge cases.

components/progress-bar/progress-bar.js

@@ -304,6 +304,11 @@
      */
     async refresh() {
 
+      // Don't write the custom property if not visible or if currently hiding.
+      if (!(this.#visible === true && this.#hiding === false)) {
+        return;
+      }
+
       await new Promise(requestAnimationFrame);
 
       html.style.setProperty(valueCustomProperty, this.#value);