It's not letting me play demo minecraft.

Put the summary of the bug you're having here

What I expected to happen was...:
Describe what you thought should happen here To go into demo minecraft

What actually happened was...:
Describe what happened here closed and opened the Launcher

Steps to Reproduce:
1. Download Minecraft Demo
2. Open the Launcher
3. Click 'Play Demo'
4. It will close and re-open 'Minecraft Demo'