[TLF] Pressing BACKSPACE key when editing a TextInput deletes a whole line

When editing a spark TextInput or TextFlow (problem should exist with TextArea as well but I didn't test), BACKSPACE key behaves incorrectly and delete the current line (if multiple lines) or the whole text instead of the previous character only.
When application is compiled with a previous version of the SDK, there is no issue (at least with 4.9 and 4.10)

Steps to reproduce:

• Add a TextInput to the stage and set its direction to RTL
• Type in some text
• Hit the BACKSPACE key to delete the last entered character

Result:
The last line of text is deleted

Expected result:
Only the last character is deleted