'Remove Member' button is shown and makes error unexpectedly

[Silver-IT]

Problem

Steps to reproduce

• [Tab1] u1 signs up, and creates a group
• [Tab2] u2 joins the group
• [Tab3] u3 joins the group, and logs out
• [Tab2] u2 creates a proposal to remove u3, DO NOT click 'Awesome' button at the last step
• [Tab1] u1 approves the proposal
• [Tab2] u2 still sees the proposal modal, and one more red button Remove Member. If u2 clicks this button, he gets error.
  

Solution

Define the workflow and implement it

• The modal should be closed as soon as the proposal is completed
• The modal should not display Remove Member button

cc: @taoeffect

[taoeffect]

Closed in #1764