[OpenGL] `g_pGamePersistent` is null during initialization of `render_rain`

Describe the bug
g_pGamePersistent is null during initialization of render_rain

To Reproduce
Steps to reproduce the behavior:

1. Apply the following patch or run with the undefined behavior sanitizer.

diff --git a/src/Layers/xrRender/light.cpp b/src/Layers/xrRender/light.cpp
index 03ba99f39..81265ce9d 100644
--- a/src/Layers/xrRender/light.cpp
+++ b/src/Layers/xrRender/light.cpp
@@ -7,6 +7,8 @@ static constexpr float RSQRTDIV2 = 0.70710678118654752440084436210485f;
 
 light::light() : SpatialBase(g_pGamePersistent->SpatialSpace)
 {
+    VERIFY(g_pGamePersistent);
+
     spatial.type = STYPE_LIGHTSOURCE;
     flags.type = POINT;
     flags.bStatic = false;

2. Start the game
3. See error

Expected behavior
Not reading from null pointers.

Screenshots, videos
N/A

BugTrap error report
Message from UBSAN:
/mnt/data/dev/xray-16/src/Layers/xrRender/light.cpp:8:49: runtime error: member access within null pointer of type 'struct IGame_Persistent'

Crash from the patch above:
FATAL ERROR

[error] Expression : g_pGamePersistent
[error] Function : light
[error] File : /mnt/data/dev/xray-16/src/Layers/xrRender/light.cpp
[error] Line : 10
[error] Description : assertion failed

stack trace:

xrDebug::Fail(bool&, ErrorLocation const&, char const*, char const*, char const*, char const*)
xray::render::render_gl::light::light()
/mnt/data/dev/xray-16/bin/x86_64/Debug/xrRender_GL.so(+0x244c0b8) [0x7ffff504c0b8]
xray::render::render_gl::CRender::CRender()
/mnt/data/dev/xray-16/bin/x86_64/Debug/xrRender_GL.so(+0x24a580d) [0x7ffff50a580d]
/mnt/data/dev/xray-16/bin/x86_64/Debug/xrRender_GL.so(+0x24a5932) [0x7ffff50a5932]
/mnt/data/dev/xray-16/bin/x86_64/Debug/xrRender_GL.so(+0x2be59f5) [0x7ffff57e59f5]
/lib64/ld-linux-x86-64.so.2(+0x549e) [0x7ffff7fc949e]
/lib64/ld-linux-x86-64.so.2(+0x55a3) [0x7ffff7fc95a3]
/lib64/ld-linux-x86-64.so.2(+0x20b60) [0x7ffff7fe4b60]

Stack trace from gdb:
xrRender_GL.so!xray::render::render_gl::light::light(xray::render::render_gl::light * const this) (/mnt/data/dev/xray-16/src/Layers/xrRender/light.cpp:10)
xrRender_GL.so!xray::render::render_gl::render_rain::render_rain(xray::render::render_gl::render_rain * const this) (/mnt/data/dev/xray-16/src/Layers/xrRender_R2/r2.h:121)
xrRender_GL.so!xray::render::render_gl::CRender::CRender(xray::render::render_gl::CRender * const this) (/mnt/data/dev/xray-16/src/Layers/xrRender_R2/r2.cpp:865)
xrRender_GL.so!__static_initialization_and_destruction_0() (/mnt/data/dev/xray-16/src/Layers/xrRender_R2/r2.cpp:20)
xrRender_GL.so!_GLOBAL__sub_I_r2.cpp(void)() (/mnt/data/dev/xray-16/src/Layers/xrRender_R2/r2.cpp:892)
xrRender_GL.so!_sub_I_65535_0.0 (Unknown Source:0)
ld-linux-x86-64.so.2![Unknown/Just-In-Time compiled code] (Unknown Source:0)

Desktop (please complete the following information):

• OS: Linux 6.13.5-2-cachyos
• OpenXRay build version d62c9b65e11ea0f2754c9e561e5f04ca6a3259b5

Additional context
Possibly introduced with 1efa85e6c8dd60b09d15b3d738590dc674a4b333

Start in src/Layers/xrRender/light.cpp and trace the render_rain construction from src/Layers/xrRender_R2/r2.h and r2.cpp. Reproduce the startup with UBSAN and inspect the static initialization path shown in the report. Done means initialization no longer reads g_pGamePersistent through a null pointer and the game starts without the reported sanitizer error.