Remove slow execution path on DefaultSearchRequestURLHandler

On DefaultSearchRequestURLHandler#handleRequest, there is an execution path that ends up calling getSearchRequestFactory().createFromParameters(null, loggedInUser, new ActionParamsImpl(parameters));.

That createFromParameters method is deprecated on SearchRequestFactory because it's very slow since it ends up calculating the context for the given query.

As we already know, calculating such context is an expensive operation that has a poor performance on large JIRA instances.

Luckily, that execution path can be removed from DefaultSearchRequestURLHandler, since it is only reached when the jql string parameter is null. After investigation, we have come to the conclusion that the only way of getting a null jql parameter is if the user plays with that url and removes it.

We should remove this execution path by handling the null case as if it was an empty jql string.