2.19: "invalid projection matrix" when SpiderVision file is created with IG+VR template

[Amerio.Stephane]

Hello, this one took me a while to isolate...

• Create a new 2.19 IG+VR cpp template (the VR part seems important...), with SpiderVision and Syncker
• Add IG, SpiderVision, Syncker on the start up command line
• Start the app, press F10 and create a default.sv file in /data
• set console_onscreen 1
• Restart the app
• The console will dump a constant stream of 
  ERROR:    Camera::setProjection: invalid projection matrix.

Apparently, the default.sv <viewport> section contains this attribute
head_pos_offset="0 2.08999991 0" 
which create this stream of error. Removing it fix the problem, until a new sv needs to be created...

Sub-question: What is this for?