bug(ios): blank keyboard in simulator and javascript errors in release@19.0.48-alpha

### Describe the bug

Versions 19.0.48-alpha and later show a blank in-app keyboard when Keyman is run in the iOS Simulator.

It seems these issues first appeared after PR #14030

When first placing the insertion point in the text area above the blank keyboard and when typing, errors appear in Safari's Web Inspector.

For example, in line 300 of ios-host.js, within the setKeymanContext() function:
`undefined is not an object (evaluating 'keyman.context.setText')
`

### Keyman apps

- [ ] Keyman for Android
- [x] Keyman for iPhone and iPad
- [ ] Keyman for Linux
- [ ] Keyman for macOS
- [ ] Keyman for Windows
- [ ] Keyman Developer
- [ ] KeymanWeb
- [ ] Other - give details at bottom of form

### Keyman version

19.0.48-alpha

### Operating system

iOS

### Device

Simulator only(?)