To reproduce:
1) Create new project
2) In Asset Store, import TextMesh Pro
3) Open Window -> TextMeshPro -> Asset Font Creator
4) Select any font but not Arial
5) Click 'Generate Font Atlas'
6) After generation, select "Arial" font
7) Click "Generate Font Atlas' twice
8) The first time it will cause an error, the second time it will regenerate the one selected in step 4 (possible bug?)
9) Close the Asset Creator window
10) Open it again
11) Repeat steps 6-7 (select Arial and generate twice)

CRASH!

Reproduced in 2017.2.0p1, 2017.3.0b4, 2018.1.0a1 (in 2018, after "Unity stopped working" prompt, the Unity stays frozen forever and even task manager a long time to kill it (>5 minutes)
Couldn't test 2017.1.1f1 because Unity crashes while importing the plugin
Couldn't test 2017.1.2p2 because after importing, the GUI is completely borked - https://i.imgur.com/PoHUZe8.png