Inventory does not update after completing challenge

[tastybento]

Description
The GUI does not update after completing a challenge until you close the GUI and reopen.

Steps to reproduce the behavior:

1. Complete challenge
2. No GUI change
3. Close GUI
4. Reopen - see challenge is done

Expected behavior
GUI should update to the latest when the challenge is done (tip - close and reopen GUI or update inventory slot)

Server Information:

[Please complete the following information:]

• YAML
• MacOS
• Java Version: Java 8
• BentoBox version: 1.2
• Addons installed?

[23:05:32 INFO]: Bentobox version: 1.2.1-SNAPSHOT
[23:05:32 INFO]: Loaded Game Worlds:
[23:05:32 INFO]: AcidIsland_world (AcidIsland)
[23:05:32 INFO]: BSkyBlock_world (BSkyBlock)
[23:05:32 INFO]: Loaded Add-Ons
[23:05:32 INFO]: BSkyBlock 1.2.0
[23:05:32 INFO]: AcidIsland 1.2-SNAPSHOT
[23:05:32 INFO]: Challenges 0.5.0-SNAPSHOT

• Other plugins? [Do '/plugins' and copy/paste from the console]

Plugins (4): WorldEdit, Essentials, BentoBox, Multiverse-Core

[tastybento]

@BONNe I made a change to fix this issue and give a good experience. Basically, just the challenge icon is updated and not the whole panel. Please try it out.