Editor: initial text not erased by DELETE (FF)

[bill]

On test_Editor.html, go to the second editor and:

1. Click to focus the editor (caret can be anywhere)
2. Type meta-a (mac) or ctrl-a (windows) to select all the text
3. Press either DELETE or a normal key. That should clear the selected text, but it doesn't.

You need to type something into the editor first and then delete etc. works.

[bill]

(In [18821]) Fix exception if a user calls attr('disableSpellCheck') before the editor's iframe has finished initializing. Fixes #9552 !strict.

[bill]

Oops, above checkin fixes #9551 not this ticket.

[bill]

Hmm, this works in 1.3, maybe I broke something recently.

[bill]

(In [18822]) Fix another regression from [18432]; on FF, can't select then delete initial text in editor. Refs #9398, fixes #9552 !strict.