XaAES 'video = xx' issues

[mikrosk]

After a very painful investigation I've collected following issues / unexplained behaviour related to XaAES video settings:

• for some reason XaAES refuses to launch in RGB
• when using NVDI, setting all SCREEN.SYS entries in ASSIGN.SYS without 'p' (i.e. 01 SCREEN.SYS) makes XaAES fail with an v_openvwk error (and reboot) (actually this bombs also in plain TOS so not really a bug)
• when using NVDI and SuperVidel's ASSIGN.SYS (i.e. all entries look like 01 SVCREEN.SYS) I'm getting memory violation when launching any GEM app (QED for instance) if and only if video = xx is specified (for instance "video = 27" but also any SV resolution); without "video = xx" everything works fine
• it seems that XaAES can't start without "video = " set to some (reasonable) value. At least on my Falcon booting in 640x480@2 colours I'm getting video init errors and reboot. Strangely, it works if NVRAM boot resolution is set to 640x480@256 colours. (see also XaAES terminates with NVDI in default/current resolution #159)

[mikrosk]

Added fourth issue.