Fix custom world rendering feature

[4z0t]

• get worldview pointer from arguments
• use OnRenderWorld of the worldview
• custom world rendering works when SetCustomRendering is set to true

Example:

viewLeft.OnRenderWorld = function(self, delta)
        UI_DrawCircle(GetMouseWorldPos(), 10, 'ffffffff', 0.3)
end
viewLeft:SetCustomRender(true)