Fix Chinese input issue

[azone]

do nothing if the text field has markedTextRange

[mats-claassen]

Please explain the issue, ideally with code to reproduce and state versions of Eureka, Xcode, iOS

[azone]

If there is no marked text, the value of the property is nil. Marked text is provisionally inserted text that requires user confirmation; it occurs in multistage text input. The current selection, which can be a caret or an extended range, always occurs within the marked text. (https://developer.apple.com/documentation/uikit/uitextinput/1614489-markedtextrange)

You should not do anything during the marked text presents.

If you want to reproduce it, just run the demo, and do the following steps:

1. input any Chinese characters and confirm the marked text
2. input Chinese characters again

After those two steps, you'll found that you can't input anymore, or very weird.