How to reproduce:
1. Build the "Multi-Display.zip" project for iOS
2. Connect extra screen to iOS device (via cable or Airplay)
3. Run the build on iOS device

Actual result: Unity crashes.

Reproducible with: 2019.3.0a11, 2019.2.0f1, 2019.1.12f1, 2019.1.0b1.
Regression introduced in: 2019.1.0b1.
Not reproducible with: 2019.1.0a14, 2019.1.0a1, 2018.4.5f1, 2018.3.14f1.

Tested with:
- iPhone 6s (iOS 11.4.1)
- iPhone 7 (iOS 10.2)
- iPhone Xr (iOS 13.0)

Notes:
- On Unity 2017.4-2018.2 multi-display causes the game view to not render anything.
- Reproducible on Metal, OpenGLES 3 and OpenGLES 2.
- Not reproducible on Android: Samsung Galaxy S10+ (SM-G975U), Android 9, CPU: Snapdragon 855 SM8150, GPU: Adreno (TM) 640

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Fixed in 2020.1.0a2, 2019.3.0b2.