backport: Fix a warning if links sticky status isn't set

- initiate its status to false when the link is created
- if not defined, initiate its status to false (can happen if the updater hasn't run)

This is a backport of https://github.com/shaarli/Shaarli/pull/1270

Original author information:

commit b790f900c937d0d8f6eccc15d2b4c26023f3d276
Author: ArthurHoaro <arthur@hoa.ro>
Date:   Sat Feb 9 14:04:16 2019 +0100

Signed-off-by: VirtualTam <virtualtam@flibidi.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/index.php b/index.php
index acfcc660..4deed197 100644
--- a/index.php
+++ b/index.php
@@ -1179,6 +1179,8 @@ function renderPage($conf, $pluginManager, $LINKSDB, $history, $sessionManager,
             $link['thumbnail'] = $thumbnailer->get($url);
         }
 
+        $link['sticky'] = isset($link['sticky']) ? $link['sticky'] : false;
+
         $pluginManager->executeHooks('save_link', $link);
 
         $LINKSDB[$id] = $link;