TracLinks to non-existent reports should have the "missing" class and should not have an href attribute

[Ryan J Ollos <ryan.j.ollos@…>]

For example, {10000}. The HTML is:

<a class="report" href="/report/10000">{10000}</a>

but should be:

<a class="missing report">{10000}</a>

resulting in:

{10000}