Placeholder appears instead of Unity logo on IOS device when DisplayP3 is selected in Color Gamut under the player settings.

Steps to repro:
1. Create a new project using Lightweight RP template.
2. Select iOS platform in Build Settings > Switch Platform.
3. Uncheck Auto Graphic APIs checkbox in Other Settings.
4. Select DisplayP3 option in Color Gamut.
5. Create a build and deploy it on IOS device.

Actual Result:
Placeholder appears instead of Unity logo on IOS device.

Occurring with iPhone 7, iPhone 7 Plus and iPhone 8.

Working Fine on: iPhone 6, iPhone 6 Plus.

Reproducible on:
2018.2.0b5, 2018.2.0b1, 2018.1.0f2, 2018.1.0b13, 2018.1.0b5.