Summary:
On switching of Graphics API for Mac in Player settings error appears in the console.
On changing from OpenGLCore to OpenGL2 Gameview becomes black.

Steps to repro:
1. Open Unity.
2. Go to Edit - Project Settings - Player.
3. Uncheck Auto Graphics API for MAC.
4. In appeared list switch OpenGLCore to OpenGL2. Press Apply.

Actual result: Gameview window is black. Error appears:
Internal: Possible leak. All textures should be removed from IdMap when destructed using RemoveTexture(TextureID texid).
If you switch back from OpenGL2 to OpenGLCore error appears again, Gameview is not black.

Expected result: Gameview is not black. Errors do not appear.

Error appearence: regression from 5.4.0b7, no error in beta6.
Black game view on switching from OpenGLCore to OpenGL2: regression since 5.4.0b4, works fine in beta3.