Cannot touch at top of screen after input japanese on UEditableTextBox on IOS

[translated comment from licensee]

This issue can be found in a IOS project using the Integrated Keyboard.
it occurs when using a Japanese keyboard on EditableTextBox.
There is no problem with English and Korean keyboards.

It seems that there is no problem with the touch input itself, as I can find log Got a keyboard call, line ###.

When the keyboard is activated, the popup UIView does not disappear completely after being called from FIOS PlatformTextField::ShowVirtualKeyboard(), so the keyboard is processing the input of a certain area at the top of the screen.

When I printed value of the CGRect.size.height in UIKeyboardFrame in Korean and English keyboard View. it is different from the value of the Japanese keyboard. the height value was 209.0 for Korean/English and 203.0 for Japanese keyboard.

As a result of this difference, when the keyboard is hidden, the keyboard view does not move enough.

1. install attached project 'touchsample' on IOS device
2. run touchsample on IOS device
3. touch at the top of the screen , and it will working well
4. input any Japanese characters on EditableTextBox
5. touch at the top of the screen , and it is no longer respond