Tolerate a missing or empty repository URL

`trim_end()` returns NULL when a repo url is empty or all slashes and
the later newline trim dereferenced it. The legacy `r=` and `p=about`
path also read the last byte of the url without checking it was set.

1 file changed, 2 insertions, 1 deletion

diff --git a/source/cmd.c b/source/cmd.c
index 7eb642c..aaf5fe5 100644
--- a/source/cmd.c
+++ b/source/cmd.c
@@ -42,7 +42,8 @@ static void about_fn(void)
 	if (ctx.repo) {
 		size_t path_info_len = ctx.env.path_info ? strlen(ctx.env.path_info) : 0;
 		if (!ctx.qry.path &&
-		    ctx.qry.url[strlen(ctx.qry.url) - 1] != '/' &&
+		    (!ctx.qry.url || !*ctx.qry.url ||
+		     ctx.qry.url[strlen(ctx.qry.url) - 1] != '/') &&
 		    (!path_info_len || ctx.env.path_info[path_info_len - 1] != '/')) {
 			char *currenturl = cgit_currenturl();
 			char *redirect = fmtalloc("%s/", currenturl);