Reproduction steps:

1. Create a New Project and import the attached font file
2. "Window" -> "TextMesh Pro" -> "Font Asset Creator"
3. Set "Source Font File" to "EmojiOneColor-apple"
4. Set "Sampling Point Size" -> "Custom Size" to '40'
5. "Generate Font Atlas"

Expected Result: Font Atlas is created
Actual Result: The Editor crashes

Reproduced with: 2019.1.0a7, 2018.3.0b8, 2018.2.14f1, 2018.1.9f2, 2017.4.14f1

Note:
Import TMP Essentials