[WEB-663] fix: project members settings flickering

[1akhanBaheti]

Problem:

1. When either the project lead or default assignee is changed, the other property automatically changes to None for a blink.
2. Default assignee & project lead container have slight differences in height when one of the property have value as None.

Solution:

1. While updating project details, one of the property value was going as undefined, so fixed it by checking for its value in currentProjectDetails.
2. Gave fixed height to both property container's.

Before:

project-members-settings-problem.mp4

After:

project-member-settings-solution.mp4

This PR is attached to WEB-663