Pressing up / down arrows in REPL loses whatever you currently have typed in the REPL

[WalterGR]

Using:

• Current Atom (1.17.0)
• Current Proto-REPL (1.4.20)
• Current Ink (0.6.5)
• Mac OS X 10.10.5

Repro:

1. Open a REPL tab.
2. Type something long in the REPL.
3. Accidentally press up or down (for example, maybe you thought you'd be selecting an autocomplete suggestion, or maybe you just fat-fingered it.)

Expected:

If there are multiple lines at the REPL prompt, up / down navigate between the lines.

If there is only 1 line in the REPL prompt, nothing happens.

Actual:

If there is one line, the text is cleared.

If there are multiple lines and Up is pressed when on the first line, or Down is pressed when on the last line, the text is cleared.

Notes:

If you catch this happening, you can Undo and get the text back.

But if you press Up Up or Down Down the text is lost completely.