Fix an NPD when handle is overwritten with nil

Call the defer function with the non nil handle, and allow the handle
to be overwritten later. Now the handle in the defer will still be
non-nil.

internal/js/modules/k6/browser/common/frame.go

@@ -500,12 +500,12 @@ func (f *Frame) waitForSelector(selector string, opts *FrameWaitForSelectorOptio
 	// an element should belong to the current execution context.
 	// otherwise, we should adopt it to this execution context.
 	if ec != handle.execCtx {
-		defer func() {
+		defer func(handle *ElementHandle) {
 			if err := handle.Dispose(); err != nil {
 				err = fmt.Errorf("disposing element handle: %w", err)
 				rerr = errors.Join(err, rerr)
 			}
-		}()
+		}(handle)
 		if handle, err = ec.adoptElementHandle(handle); err != nil {
 			return nil, fmt.Errorf("waiting for selector %q: adopting element handle: %w", selector, err)
 		}