[FIX] Handle database errors properly (#650)

app/containers/MessageBox/index.js

app/lib/methods/getCustomEmojis.js

app/lib/methods/getSettings.js

app/lib/methods/loadMessagesForRoom.js

app/lib/methods/loadMissedMessages.js

app/lib/methods/sendFileMessage.js

app/lib/methods/subscriptions/rooms.js

app/lib/rocketchat.js