fixed incorrect type of handle for some WIN32 file operations

The return type is intptr_t which may be 64bit. Stuffing that into an int can lead to an overflow, which then can lead to the error check (if handle < 0) failing.
Which has caused me to need to restart the game soooo many times already... Like some sort of old car with a broken starter.
only try to draw PXS when there is something drawable

This fixes a crash for me, where the vertex vectors were simply empty and pixVtx[0] caused a subscript-error.
Script GUIs: fixed last remaining old method names
Script GUIs: fixed saving & loading