gitweb: add link to graph

error.tmpl wasn't consistent with other templates in gitweb in
that it was missing a "graph" link. This commit makes it consistent.

mercurial/templates/gitweb/error.tmpl

@@ -17,6 +17,7 b''
 <a href="{url|urlescape}summary{sessionvars%urlparameter}">summary</a> |
 <a href="{url|urlescape}shortlog{sessionvars%urlparameter}">shortlog</a> |
 <a href="{url|urlescape}log{sessionvars%urlparameter}">changelog</a> |
+<a href="{url|urlescape}graph{sessionvars%urlparameter}">graph</a> |
 <a href="{url|urlescape}tags{sessionvars%urlparameter}">tags</a> |
 <a href="{url|urlescape}bookmarks{sessionvars%urlparameter}">bookmarks</a> |
 <a href="{url|urlescape}branches{sessionvars%urlparameter}">branches</a> |