Segfault when touching a checkpoint in editor playtesting with checkpoint autosaving enabled

[InfoTeddy]

To reproduce, you need to not have loaded the levels list first before entering the editor.

This has been happening since #1174 was merged. The reason is because of the following:

VVVVVV/desktop_version/src/Game.cpp

Line 852 in a0bd2f3

bool success = map.custommode ? customsavequick(cl.ListOfMetaData[playcustomlevel].filename) : savequick();

Obviously, we should not be trying to save quicksaves during in-editor playtesting. We probably don't even want auto-quicksaves during command-line playtesting either.