BUG/MINOR: ssl_ckch: Fix another possible uninitialized value

Commit d6c66f06a ("MINOR: ssl_ckch: Remove service context for "set ssl
crl-file" command") introduced a regression leading to a build error because
of a possible uninitialized value. It is now fixed.

This patch must be backported as far as 2.5.
diff --git a/src/ssl_ckch.c b/src/ssl_ckch.c
index e882c1a..9d7775a 100644
--- a/src/ssl_ckch.c
+++ b/src/ssl_ckch.c
@@ -3221,8 +3221,8 @@
 /* Parsing function of `set ssl crl-file` */
 static int cli_parse_set_crlfile(char **args, char *payload, struct appctx *appctx, void *private)
 {
-	struct cafile_entry *old_crlfile_entry;
-	struct cafile_entry *new_crlfile_entry;
+	struct cafile_entry *old_crlfile_entry = NULL;
+	struct cafile_entry *new_crlfile_entry = NULL;
 	char *err = NULL;
 	int errcode = 0;
 	struct buffer *buf;