Document that EnableUserControl(true) fixes UI after DialogClear(dlg) on still displayed dialog

[Slayer95]

I met the broken UI issue randomly, and tried SetUserControlForceOn(bj_FORCE_ALL_PLAYERS) to fix it, and was fortunate enough that it worked.

Then I randomly found the docs on DialogClear:

Completely clears the dialog, its title and buttons, even if it is already open.
You must hide the dialog first, else the player will need to quit the game, because they will be unable to click anything or send a chat message.

Which agrees with the context in which the UI bug happened.

Goal is that these functions should refer to each other, in case someone experiences the same.

Note: SetUserControlForceOn(bj_FORCE_ALL_PLAYERS) is equivalent to EnableUserControl(true).