[Task] Let's make Assigned Member Mandatory field while creating the Task

[drasticdpk]

Reference

Current Behaviour : During closing the task it is asking assigned member.

[coderhacker]

this is not fixed on Production:

[vikasrohit]

I don't think we attempted to fix it @lakshmiathreya, is there any release after 0.8.0 for which we are doing testing round?