In DesktopTextInputService, ignore call to stopInput()

[m-sasha]

#1974, adds calls of startInput() (no-argument version) and stopInput to DesktopTextInputService.

Unfortunately, DesktopTextInputService was not prepared for this scenario, as it never expected startInput() (the version without arguments) to be called. It would then call PlatformComponent.disableInput() on stopInput(), causing this to be called twice (another time by DesktopTextInputService2).

This PR fixes DesktopTextInputService to ignore stopInput calls unless the correct startInput function was called.

Release Notes

N/A