How to reproduce:
1. Open the attached project
2. There is a scene which has UI button set to Screen Space - Overlay and Main Camera is deleted
3. Build and run test scene on Android device
Result: Notice that UI is corrupted

Reproducible: 5.3.7p4, 5.4.4p2, 5.5.1p3, 5.6.0b7

DUT(reproducible):
LG G5 [LG-H850], Qualcomm Snapdragon 820, Adreno 530, OS 6.0.1
Google Nexus 4 [mako], Qualcomm Snapdragon S4 Pro, Adreno 320, 5.1.1
Motorola Moto G (4), Qualcomm Snapdragon 617, Adreno (TM) 405, OS 6.0.1

DUT(not reproducible):
Samsung Galaxy S 5 Neo [SM-G903F], Samsung Exynos 7 Octa, ARM Mali-T720, OS 6.0.1
Meizu MX5, PowerVR Rogue G6200, MediaTek, OS 5.0.1
iPhone 6+ (iOS 10.1)

By Design: to get an expected behavior one should use camera in the scene so it clears at least once either the color or the depth buffer. Otherwise on some GPUs not clearing the screen might result in the contents of it being undefined in the next frame. On some systems, the screen may contain the previous frame image, a solid black screen, or random colored pixels.