Committing a candidate text with ENTER key in a Japanese IME window results in a new line inserted in the text.

To reproduce on Mac:
- add a Japanese keyboard in Settings -> Keyboard -> Text Input -> Input Sources (Japanese - Romaji)
- run the attached application
- click on the beginning of the text (before "<insert text here")
- switch to Japanese keyboard and type "arigatou"
- pick a candidate (ありがとう) and press ENTER to commit

Expected:
-- the candidate replacement text should be inserted on the same line
Observed:
-- the candidate text is inserted along with an extra new line


This may or may not be a Mac-only issue.
Can be seen as early as openjfx19.0.2.1, and probably earlier.