[r302] Player passes through 3D floor with zero x-y momentum

[carlcyber]

This happens when I am playing zportal, the demo file is using zportal as a base. To reproduce the bug, just simply make a portal in the black sector and then make another portal right in the player's position (the player should stand still at that time) and will be teleported right away to the other one. Then you will see the player falls through every 3D floor until hitting the real ground. At that time, you can see the marble-textured sector which is impossible to get there in normal ways.
Demo file

[Graf Zahl]

fixed (also in ZDoom for 3DMidtex textures)