Unity crashes when pressing "Expresion Evaluator" in MonoDevelop.
Side note: It also crashes using Visual studio.

Steps to reproduce(in MonoDevelop):
--- Alternatively you can watch 1 attached link.
1. Open my attached project "Repro MonoDevCrash" using 5.3.4f1 version.
2. Press play button in the toolbar.
3. Open "scr" script using MonoDevelop.
--- Check if "Editor Attaching" is selected in "Preferences" menu (Check 2 attached link).
4. Place "Breakpoint" in "Update()" function (only if it doesn't exist). See attached 1 link for example.
5. Start debugging this script.
6. Right click agent (in 6 line) and choose "Expression Evaluator".
7. In the new table double click on "agent". It should crash or freeze.

Side note: Check 3 attached link to also reproduce in Visual studio.

Reproduced in: 5.4.21b, 5.0.3f2, 5.3.4f1.

Attached links:
1. http://recordit.co/PU4TrUL119
2. https://gyazo.com/c34700cb1598610558610428656fb329
3. http://recordit.co/M2AoGEtPGy