Line management icon disappears from main menu bar when disallow player changes.

Oops, where is the icon? (´・ω・`)
There should have been Line management icon in the place indicated by the red arrow.
You can use the shortcut key though.
EDIT:
This seems to be caused by the Map Editing Tools icon was there.
Locking the player will switch public player to the nomal player, but the Line management icon will not revive and the Map Editing Tools icon will be banished.
After saving and reloading or restarting the game, the line management icon will revive.
EDIT2:
Sorry I jumped to conclusion, this seems to be a bug originated from standard.