Fixes contextual menu iPad presentation crashes

[etoledom]

Closes #745

Description

Small PR which fixes a crash on the demo app regarding presenting menu items on iPad.

Testing Steps

• Run the demo app on an iPad
• Go through all demo screens in the UIKit context.
• Select all available option menus
  • Check that there are no crashes.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Gravatar Prototype Build by scanning the QR code below to install the corresponding build.

	App Name	Gravatar Prototype Build
	Build Number	2356
	Version	PR #757
	Bundle ID	com.automattic.gravatar-sdk-demo-uikit.prototype-build
	Commit	d6405d0
	Installation URL	3jftbjig8j1f8

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[pinarol]

Looks great 🎉