Minor menu UI bug

[SigmaEpsilon]

I cannot access other menu items without first explicitly closing any existing windows.

Steps:
1. Select one of the items in the lower-right menu (Overview/Research/Codex/Menu).
2. After the window appears, select a different item.

Expected Results:
The existing window disappears, and the newly-select window appears.

Actual Results:
The existing window stays open until the user explicitly closes it.