gitweb: Fix shortlog only showing HEAD revision.

My change in 190d7fd had a small bug
found by Michael Krufky which caused the passed in hash value to be
ignored, so shortlog would only show the HEAD revision.

Signed-off-by: Robert Fitzsimons <robfitz@273k.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

gitweb/gitweb.perl

@@ -4423,7 +4423,7 @@ sub git_shortlog {
 	}
 	my $refs = git_get_references();
 
-	my @commitlist = parse_commits($head, 101, (100 * $page));
+	my @commitlist = parse_commits($hash, 101, (100 * $page));
 
 	my $paging_nav = format_paging_nav('shortlog', $hash, $head, $page, (100 * ($page+1)));
 	my $next_link = '';