Light2D with shadows enabled near an occluder displays errors instead of shadows

[eon-s]

Ubuntu 17.04 - Godot version: 3 master
Using Nvidia 375.39 drivers.

Issue description:
Light2D starts spamming "meseges" when shadow is enabled and a LightOccluder2D is in range.
This happens in editor.

Steps to reproduce:

• Create a LightOccluder2D.
• Add a Light2D with the occluder in range.
• Enable shadows on the Light2D.
• Watch the terminal output get eclipsed by meseges.

---

The message spammed when turning shadows in editor is:

mesege
ERROR: _gl_debug_print: GL ERROR: Source: OpenGL	Type: Error	ID: 1282Severity: High	Message: GL_INVALID_OPERATION error generated. Array object is not active.
   At: drivers/gles3/rasterizer_gles3.cpp:123.

---

Turning on the shadow while running got an extra error sometimes between the other:

mesege
ERROR: _gl_debug_print: GL ERROR: Source: OpenGL	Type: Error	ID: 1282Severity: High	Message: GL_INVALID_OPERATION error generated. Invalid VAO/VBO/pointer usage.
   At: drivers/gles3/rasterizer_gles3.cpp:123.

---

And this error too but saw it while running other things (sometimes while opening the editor) so I guess it is not related

mesege
ERROR: _gl_debug_print: GL ERROR: Source: OpenGL	Type: Performance	ID: 131218	Severity: Medium	Message: Program/shader state performance warning: Vertex shader in program 4 is being recompiled based on GL state.
   At: drivers/gles3/rasterizer_gles3.cpp:123.

[Zireael07]

"mesege" :D :D :D