Segementation fault on r_showLightGrid 1.

[Viech]

The client running current master of c5bb4b5 crashes the moment when I enable r_showLightGrid. Happens on both Intel (mesa) and Nvidia (proprietary) graphics.

Thread 1 (Thread 0x7ffff7fae780 (LWP 32268)):
#0  ShaderRequiresCPUDeforms (shader=shader@entry=0x0) at /home/eris/src/Unvanquished/src/engine/renderer/tr_shade_calc.cpp:914
No locals.
#1  0x0000000000563eff in Tess_Begin (stageIteratorFunc=0x55849c <Tess_StageIteratorDebug()>, stageIteratorFunc2=stageIteratorFunc2@entry=0x0, 
surfaceShader=surfaceShader@entry=0x0, lightShader=lightShader@entry=0x0, skipTangentSpaces=skipTangentSpaces@entry=1, skipVBO=skipVBO@entry=0, lightmapNum=-1, fogNum=0) 
at /home/eris/src/Unvanquished/src/engine/renderer/tr_shade.cpp:409
        state = 0x0
        isSky = <optimized out>
#2  0x00000000005192ea in RB_RenderDebugUtils () at /home/eris/src/Unvanquished/src/engine/renderer/tr_backend.cpp:3818
        z = 0
        x = <optimized out>
        k = <optimized out>
        tmp = {1.40129846e-45, 0, 0}
        tmp2 = {8.40779079e-45, 0, 7.00072731e-17}
        tetraVerts = {{7.19205563e-38, 0, 1, 2.80259693e-45}, {0.00249999994, 0.00444444455, 7.45311977e-39, 0}, {0.00499999989, 0, 0, 0}, {0, 0.0088888891, 0, 0}}
        y = 0
        tmp3 = {1.18789663e-37, 0, 0}
        length = <optimized out>
#3  0x000000000051c2b4 in RB_RenderView () at /home/eris/src/Unvanquished/src/engine/renderer/tr_backend.cpp:4599
        clearBits = <optimized out>
        startTime = 0
        endTime = <optimized out>
#4  0x000000000051f16d in RB_DrawView (data=data@entry=0x7fffed12c054) at /home/eris/src/Unvanquished/src/engine/renderer/tr_backend.cpp:5333
        cmd = 0x7fffed12c054
#5  0x00000000005206fa in RB_ExecuteRenderCommands (data=0x7fffed12c054, data@entry=0x7fffed12c034) at 
/home/eris/src/Unvanquished/src/engine/renderer/tr_backend.cpp:5751
        t1 = 17910
        t2 = <optimized out>
#6  0x000000000052bc64 in R_IssueRenderCommands (runPerformanceCounters=1) at /home/eris/src/Unvanquished/src/engine/renderer/tr_cmds.cpp:183
        cmdList = 0x7fffed12c034
        __PRETTY_FUNCTION__ = "void R_IssueRenderCommands(qboolean)"
#7  0x000000000052c69c in RE_EndFrame (frontEndMsec=0x0, backEndMsec=0x0) at /home/eris/src/Unvanquished/src/engine/renderer/tr_cmds.cpp:862
        cmd = 0x1ae76c0 <s_worldData>
#8  0x00000000004f8db7 in SCR_UpdateScreen () at /home/eris/src/Unvanquished/src/engine/client/cl_scrn.cpp:787
        recursive = 1
#9  0x00000000004f43b7 in CL_Frame (msec=14) at /home/eris/src/Unvanquished/src/engine/client/cl_main.cpp:3670
No locals.
#10 0x000000000044b3ad in Com_Frame (GetInput=0x59ae21 <IN_Frame()>, DoneInput=0x59aecd <IN_FrameEnd()>) at 
/home/eris/src/Unvanquished/src/engine/qcommon/common.cpp:2374
        msec = 14
        timeBeforeEvents = 0
        timeBeforeClient = 0
        timeAfter = 0
        timeBeforeFirstEvents = 0
        timeBeforeServer = 0
        minMsec = 8
        lastTime = 17907
        watchdogTime = 0
        watchWarn = 0
#11 0x0000000000462c5a in main (argc=18, argv=0x7fffffffe998) at /home/eris/src/Unvanquished/src/engine/sys/sys_main.cpp:667
        i = 18
        commandLine = "\000set vm.game.type 2 \000set vm.sgame.type 2 \000set fs_basepath /usr/share/unvanquished \000set fs_extrapath . \000set fs_extrapaks \"assets 
git\" \000devmap plat23 ", '\000' <repeats 875 times>
        ver = {major = 2 '\002', minor = 0 '\000', patch = 3 '\003'}
        curses = 1

[Kangz]

Fixed in c6e5c42.