alternatives: fix a warning.

lib/package_alternatives.c

@@ -102,7 +102,7 @@ create_symlinks(struct xbps_handle *xhp, xbps_array_t a, const char *grname)
 	cnt = xbps_array_count(a);
 	for (i = 0; i < cnt; i++) {
 		xbps_string_t str;
-		char *l, *lnk, *tgt;
+		char *l, *lnk, *tgt = NULL;
 		const char *tgt0;
 		int rv;