I did not know why "cg_leiEnhancement 1" caused the game to crash.
Before I started debugging I just ran through tr_particles.c and fixed a lot of warnings. This also fixed my problem.
I think the critical part was:
```
-int reallyactive;
+particle_t* reallyactive;
```
The diff makes it a bit hard but another change was:
```
else if (p->colortype = P_INDEXED)
```
to
```
else if (p->colortype == P_INDEXED)
```
and:
```
-vec3_t color;
+vec4_t color;
```
dd2ce7ca1a