Crash when opening default lighting config dialog

[MarianoGnu]

Operating system or device - Godot version:
Xubuntu - Godot 3.0 (master)

Issue description:
When i wanted to change the default lighting on a 3D project the engine crashed with a segfault, i found the exact reason for this but could not fix it since i have no idea of what the value of these variables are suposed to be:
crash happens in rasterizer_scene_gles3.cpp line 3066:
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, storage->frame.current_rt->effects.mip_maps[0].sizes[0].fbo);
the reason of the crash is because storage->frame.current_rt->effects.mip_maps[0].sizes is a null VectorMipMaps::Size

Steps to reproduce:
Open a new, or any project, go to Spatial Editor and open the View menu and select Configuration

[reduz]

This is fixed now