Godot: [GridMap] Cannot edit grids in the 3D viewport

[HummusSamurai]

Operating system or device - Godot version:
Fedora 26 - Godot 3 master.

Issue description:

I am unable to edit the gridmap tiles.
When I click on the GridMap node, the side menu for the tiles shows up properly and I can select them, but clicking on the world does not place tiles.

Steps to reproduce:
Try to edit the grid cells.

Link to minimal example project:

The platformer 3D demo.

[akien-mga]

Just a hunch, but it might be related to @kubecz3k's recent changes to improve the usability of selecting spatial objects in the viewport.

[HummusSamurai]

Note that this bug is also present on the godot 3 alpha, so it is not related to the recent changes related to @kubecz3k

Edit: Jinx @akien-mga :b

[reduz]

this should be fixed now, closing