a temporary fix for issue 4120

[alsammak-array]

Fixes #4120

a workaround is to read the body and reset it to {} inside BindJSON(args)

// BindJSON is a shortcut for c.MustBindWith(obj, binding.JSON).
func (c *Context) BindJSON(obj any) error {

	body, err := io.ReadAll(c.Request.Body)
	if err != nil {
		return fmt.Errorf("failed to read body: %v", err)
	}

	// If the body is empty, set it to {}
	if len(body) == 0 {
		body = []byte("{}")
		c.Request.Body = io.NopCloser(bytes.NewBuffer(body)) // Set to {} to trigger the error
		return c.MustBindWith(obj, binding.JSON)
	}

	// Restore the body since it was read
	c.Request.Body = io.NopCloser(bytes.NewBuffer(body))
	return c.MustBindWith(obj, binding.JSON)
}

the output should be as expected in the issue.