How to reproduce:
1. Download user's attached project
2. In the project open the Scene called "Main"
3. Play the Scene and you will see the simple UI text field
4. Enter any string in that text field
-- crash occurs

Reproducible with: 2017.4.11f1, 2018.1.9f2 ,2018.2.7f1, 2018.3.0a11

Note: In most versions, I was able to reproduce the crash just by playing the Scene.

First four lines of the stack trace:
0x00007FF8A024109A (Molecular_Geometry) Main
0x00000000394CC19C (Mono JIT Code) (wrapper managed-to-native) Molecule:Main (string)
0x00000000394CBFA4 (Mono JIT Code) [C:\Users\STUDENT\Desktop\2018.2\Assets\Molecule.cs:32] Molecule:Update ()
0x0000000033FE7192 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)