Add test case for setting editor value before focusing it, refs #9151.
Also removing related &nbsp code that no longer seems necessary.
(cherry picked from commit 66633d40e085c5a334164225ace5985afdb78603)
Add isLoaded check to RichText#getValue to avoid errors when the iframe has not yet loaded.
Fixes #15134.
(cherry picked from commit 4dc879a433b3c3db4310011cf28e13edd0801139)