[Core] Verify the presence of the array keys before accessing them. Fixes  #588
[Core] Verify the presence of the array keys before accessing them.
Fixes  #588

sebsauvage/rss-bridge,ORelio/rss-bridge,Riduidel/rss-bridge,teromene/rss-bridge,RSS-Bridge/rss-bridge,ORelio/rss-bridge,simonbru/rss-bridge,teromene/rss-bridge,kranack/rss-bridge,kranack/rss-bridge,ORelio/rss-bridge,simonbru/rss-bridge,kranack/rss-bridge,kranack/rss-bridge,Frenzie/rss-bridge,GregThib/rss-bridge,Frenzie/rss-bridge,Riduidel/rss-bridge,RSS-Bridge/rss-bridge,RSS-Bridge/rss-bridge,Riduidel/rss-bridge