Reproduction steps:
1. Open the attached project "TMPro_Disappearing_Text.zip";
2. Open the Main scene;
3. Notice that it is not saved;
4. Try to save scene (via cmd+s or via File-Save Scene);
5. Notice that the scene is still marked as dirty and try to save it once again.

Expected results: the scene is saved.
Actual results: the scene is saved, but all text disappears from the game view.

Reproducible on: 2017.4.3f1, 2018.1.0f2, 2018.1.4f1, 2018.2.0b7, 2018.3.0a1.
Not reproducible on: 2017.4.2f2 or lower.