Add extra guards against segfault

[Rainyan]

Description

Add some safety checks before using these pointers, because this area had segfaulted for v8.0-prealpha (Linux):

Trace:

Program terminated with signal SIGSEGV, Segmentation fault.
warning: Section `.reg-xstate/4255' in core file too small.
#0  0xdd621cc3 in CNEOHud_GhostMarker::DrawNeoHudElement (this=0x15ad4800) at /home/runner/work/neo/neo/mp/src/game/client/neo/ui/neo_hud_ghost_marker.cpp:177
[Current thread is 1 (Thread 0xf5be2000 (LWP 4255))]
(gdb) frame 1
#1  0xdd766c0f in vgui::Panel::PaintTraverse (this=0x15ad4848, repaint=<optimized out>, allowForce=true) at /home/runner/work/neo/neo/mp/src/vgui2/vgui_controls/Panel.cpp:1224
(gdb) frame 1
#1  0xdd766c0f in vgui::Panel::PaintTraverse (this=0x15ad4848, repaint=<optimized out>, allowForce=true) at /home/runner/work/neo/neo/mp/src/vgui2/vgui_controls/Panel.cpp:1224
(gdb) frame 0
#0  0xdd621cc3 in CNEOHud_GhostMarker::DrawNeoHudElement (this=0x15ad4800) at /home/runner/work/neo/neo/mp/src/game/client/neo/ui/neo_hud_ghost_marker.cpp:177

The lines referenced: https://github.com/NeotokyoRebuild/neo/blob/v8.0-prealpha/mp/src/game/client/neo/ui/neo_hud_ghost_marker.cpp#L176-L177

Toolchain

• Linux GCC Distro Native [Mint 21.3 Cinnamon, gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0]

Linked Issues

None