fix: setState Assertion Error in Calendar View

[r4khul]

bug:
setState accepts a sync callback, but here it was a async callback - so flutter will ping it as a assertion error
[so basically clicking the chip will not perform anything]

log: Another exception was thrown: setState() callback argument returned a Future.

fix:

• called the async func before hand & and then used setState to revalidate for the next build
• plus moved the switch case outside of the async - so we can have a optimistic ui update - while the func takes its time to write to isar