bug(ios): text disappears when rotating device to landscape

**Describe the bug**
While typing using the Keyman system keyboard in iOS, the text disappears when the device is rotated from portrait orientation to landscape. (Rotating from landscape to portrait has no effect on the currently typed text.)

**To Reproduce**
1. Run Keyman on a real device or in the simulator.
2. Open Safari and click on the url textedit to bring up the system keyboard.
3. Choose the Keyman menu from the keyboard to activate Keyman's system keyboard.
4. Hold the device in the portrait orientation.
5. Type a few characters.
6. Rotate to the landscape orientation.
7. See that the text you had typed has disappeared.

**Expected behavior**
The typed text should be retained after rotating the device.