Unable to backspace last character on JS target in FlxInputText and FlxUIInputText

[maximryzhov]

• haxe: 4.2.5
• flixel: 4.11.0
• flixel-ui: 2.4.0

Steps to reproduce:

1. Add a FlxInputText widget to an empty state
2. Build HTML5 target
3. Input "hello"
4. Hit Backspace 5 times

Expected result: the input is cleared
Actual result: the first character ('h') remains in the input field until a new character is entered.

[Geokureli]

FlxInuptText is getting a rewrite on 5.0.0 thanks to ShaharMS