[z2021] Assert correct loading of GO_TYPE_CAPTURE_POINT

This will assert controlled behaviour when loading a `gameobject_template` entry of type Capture Point with bad data

Signed-off-by: Schmoozerd <schmoozerd@scriptdev2.com>
Signed-off-by: Nighoo <nighoo@overninethousand.de>

(based on commit c5e609c)

(cleaned version of 7fddbba)

(based on commit [s1630] - 71dce5f)