segfault fix on some bogus requests

ctx.qry.head can be NULL in some cases due to bad requests
by weird bots.  I managed to reproduce with:

   PATH_INFO=/repo.git/shop.php QUERY_STRING=id=

Signed-off-by: Eric Wong <normalperson@yhbt.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/ui-shared.c b/ui-shared.c
index 3e9282f..d7d75bf 100644
--- a/ui-shared.c
+++ b/ui-shared.c
@@ -294,7 +294,7 @@ void cgit_log_link(const char *name, const char *title, const char *class,
         char *delim;
 
         delim = repolink(title, class, "log", head, path);
-        if (rev && strcmp(rev, ctx.qry.head)) {
+        if (rev && ctx.qry.head && strcmp(rev, ctx.qry.head)) {
                 html(delim);
                 html("id=");
                 html_url_arg(rev);
@@ -338,7 +338,7 @@ void cgit_commit_link(char *name, const char *title, const char *class,
         char *delim;
 
         delim = repolink(title, class, "commit", head, path);
-        if (rev && strcmp(rev, ctx.qry.head)) {
+        if (rev && ctx.qry.head && strcmp(rev, ctx.qry.head)) {
                 html(delim);
                 html("id=");
                 html_url_arg(rev);