godot: Crash when running sqrt(-1) and log(-1)

Operating system or device - Godot version: Linux. Godot 2.1.4 at commit 171d8a5.

Issue description: Godot crashes when trying to run sqrt(-1) or log(-1).

Steps to reproduce:

1. Create a new project, add a node and a script.
2. Put print(sqrt(-1)) or print(log(-1)) under _ready().
3. Run the scene.
4. The editor will crash.

Additional info: Terminal output when trying to run the scene:

ERROR: operator[]: SEVERE: Index p_index out of size (size()).
   At: core/vector.h:136.

When I open godot, select the project and click the edit button, the same error appears and the program freezes.

This bug is not on 2.1.3.