[epiphany/gnome-3-28] Fix a -Wmaybe-uninitialized warning

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 776379b123f525c5ecbae271a618637592fa0e82
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Sun Sep 2 15:24:12 2018 -0500

    Fix a -Wmaybe-uninitialized warning

 lib/sync/ephy-sync-service.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/lib/sync/ephy-sync-service.c b/lib/sync/ephy-sync-service.c
index aa9cbe810..cbcb61aa8 100644
--- a/lib/sync/ephy-sync-service.c
+++ b/lib/sync/ephy-sync-service.c
@@ -2111,7 +2111,7 @@ get_crypto_keys_cb (SoupSession *session,
   JsonObject *json = NULL;
   GError *error = NULL;
   const char *payload;
-  char *crypto_keys;
+  char *crypto_keys = NULL;
   guint8 *kb = NULL;
 
   if (msg->status_code == 404) {