Fixed rquickExpr to require 1 or more chars for ID

jQuery's `rquickExpr` allows for an ID with zero or more characters. An ID with zero characters isn't useful for fetching an element from the DOM, and `getElementById` will throw an error in Firefox, but not in Chrome.

While a selector like `$("#")` is unlikely to be manually written, it's more likely to be encountered with generated selectors.

The `rquickExpr` in Sizzle does require at least one character after `#`, so this will bring uniformity to the optimization.

Sizzle line 135: https://github.com/jquery/sizzle/blob/709e1db5bcb42e9d761dd4a8467899dd36ce63bc/src/sizzle.js#L135